OBJECTIVE

Most individuals with type 2 diabetes also have obesity, and treatment with some diabetes medications, including insulin, can cause further weight gain. No approved chronic weight management medications have been prospectively investigated in individuals with overweight or obesity and insulin-treated type 2 diabetes. The primary objective of this study was to assess the effect of liraglutide 3.0 mg versus placebo on weight loss in this population.

RESEARCH DESIGN AND METHODS

Satiety and Clinical Adiposity—Liraglutide Evidence (SCALE) Insulin was a 56-week, randomized, double-blind, placebo-controlled, multinational, multicenter trial in individuals with overweight or obesity and type 2 diabetes treated with basal insulin and ≤2 oral antidiabetic drugs.

RESULTS

Individuals were randomized to liraglutide 3.0 mg (n = 198) or placebo (n = 198), combined with intensive behavioral therapy (IBT). At 56 weeks, mean weight change was –5.8% for liraglutide 3.0 mg versus –1.5% with placebo (estimated treatment difference –4.3% [95% CI –5.5; –3.2]; P < 0.0001). With liraglutide 3.0 mg, 51.8% of individuals achieved ≥5% weight loss versus 24.0% with placebo (odds ratio 3.41 [95% CI 2.19; 5.31]; P < 0.0001). Liraglutide 3.0 mg was associated with significantly greater reductions in mean HbA_1c and mean daytime glucose values and less need for insulin versus placebo, despite a treat-to-glycemic-target protocol. More hypoglycemic events were observed with placebo than liraglutide 3.0 mg. No new safety or tolerability issues were observed.

CONCLUSIONS

In individuals with overweight or obesity and insulin-treated type 2 diabetes, liraglutide 3.0 mg as an adjunct to IBT was superior to placebo regarding weight loss and improved glycemic control despite lower doses of basal insulin and without increases in hypoglycemic events.

OBJECTIVE

The effect of early-life antibiotic treatment on the risk of type 1 diabetes is debated. This study assessed this question, applying a register-based design in children up to age 10 years including a large sibling-control analysis.

RESEARCH DESIGN AND METHODS

All singleton children (n = 797,318) born in Sweden between 1 July 2005 and 30 September 2013 were included and monitored to 31 December 2014. Cox proportional hazards models, adjusted for parental and perinatal characteristics, were applied, and stratified models were used to account for unmeasured confounders shared by siblings.

RESULTS

Type 1 diabetes developed in 1,297 children during the follow-up (median 4.0 years [range 0–8.3]). Prescribed antibiotics in the 1st year of life (23.8%) were associated with an increased risk of type 1 diabetes (adjusted hazard ratio [HR] 1.19 [95% CI 1.05–1.36]), with larger effect estimates among children delivered by cesarean section (P for interaction = 0.016). The association was driven by exposure to antibiotics primarily used for acute otitis media and respiratory tract infections. Further, we found an association of antibiotic prescriptions in pregnancy (22.5%) with type 1 diabetes (adjusted HR 1.15 [95% CI 1.00–1.32]). In general, sibling analysis supported these results, albeit often with statistically nonsignificant associations.

CONCLUSIONS

Dispensed prescription of antibiotics, mainly for acute otitis media and respiratory tract infections, in the 1st year of life is associated with an increased risk of type 1 diabetes before age 10 years, most prominently in children delivered by cesarean section.

OBJECTIVE

No study has reported global disability burden estimates for individual diabetes-related lower-extremity complications (DRLECs). The Global Burden of Disease (GBD) study presents a robust opportunity to address this gap.

RESEARCH DESIGN AND METHODS

GBD 2016 data, including prevalence and years lived with disability (YLDs), for the DRLECs of diabetic neuropathy, foot ulcer, and amputation with and without prosthesis were used. The GBD estimated prevalence using data from systematic reviews and DisMod-MR 2.1, a Bayesian meta-regression tool. YLDs were estimated as the product of prevalence estimates and disability weights for each DRLEC. We reported global and sex-, age-, region-, and country-specific estimates for each DRLEC for 1990 and 2016.

RESULTS

In 2016, an estimated 131 million people (1.8% of the global population) had DRLECs. An estimated 16.8 million YLDs (2.1% global YLDs) were caused by DRLECs, including 12.9 million (95% uncertainty interval 8.30–18.8) from neuropathy only, 2.5 million (1.7–3.6) from foot ulcers, 1.1 million (0.7–1.4) from amputation without prosthesis, and 0.4 million (0.3–0.5) from amputation with prosthesis. Age-standardized YLD rates of all DRLECs increased by between 14.6% and 31.0% from 1990 estimates. Male-to-female YLD ratios ranged from 0.96 for neuropathy only to 1.93 for foot ulcers. The 50- to 69-year-old age-group accounted for 47.8% of all YLDs from DRLECs.

CONCLUSIONS

These first-ever global estimates suggest that DRLECs are a large and growing contributor to the disability burden worldwide and disproportionately affect males and middle- to older-aged populations. These findings should facilitate policy makers worldwide to target strategies at populations disproportionately affected by DRLECs.

Impaired baroreflex sensitivity (BRS) predicts cardiovascular mortality and is prevalent in long-term diabetes. We determined spontaneous BRS in patients with recent-onset diabetes and its temporal sequence over 5 years by recording beat-to-beat blood pressure and R-R intervals over 10 min. Four time domain and four frequency domain BRS indices were computed in participants from the German Diabetes Study baseline cohort with recent-onset type 1/type 2 diabetes (n = 206/381) and age-matched glucose-tolerant control subjects (control 1/control 2: n = 65/83) and subsets of consecutive participants with type 1/type 2 diabetes who reached the 5-year follow-up (n = 84/137). Insulin sensitivity (M-value) was determined using a hyperinsulinemic-euglycemic clamp. After appropriate adjustment, three frequency domain BRS indices were reduced in type 2 diabetes compared with control 2 and were positively associated with the M-value and inversely associated with fasting glucose and HbA_1c (P < 0.05), whereas BRS was preserved in type 1 diabetes. After 5 years, a decrease in one and four BRS indices was observed in patients with type 1 and type 2 diabetes, respectively (P < 0.05), which was explained by the physiologic age-dependent decline. Unlike patients with well-controlled recent-onset type 1 diabetes, those with type 2 diabetes show early baroreflex dysfunction, likely due to insulin resistance and hyperglycemia, albeit without progression over 5 years.

Advances in small RNA sequencing have revealed the enormous diversity of small noncoding RNA (sRNA) classes in mammalian cells. At this point, most investigators in diabetes are aware of the success of microRNA (miRNA) research and appreciate the importance of posttranscriptional gene regulation in glycemic control. Nevertheless, miRNAs are just one of multiple classes of sRNAs and likely represent only a minor fraction of sRNA sequences in a given cell. Despite the widespread appreciation of sRNAs, very little research into non-miRNA sRNA function has been completed, likely due to some major barriers that present unique challenges for study. To emphasize the importance of sRNA research in cardiometabolic diseases, we highlight the success of miRNAs and competitive endogenous RNAs in cholesterol and glucose metabolism. Moreover, we argue that sequencing studies have demonstrated that miRNAs are just the tip of the iceberg for sRNAs. We are likely standing at the precipice of immense discovery for novel sRNA-mediated gene regulation in cardiometabolic diseases. To realize this potential, we must first address critical barriers with an open mind and refrain from viewing non-miRNA sRNA function through the lens of miRNAs, as they likely have their own set of distinct regulatory factors and functional mechanisms.

First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Sonu S. Baral is first author on ‘Nucleolar stress in Drosophila neuroblasts, a model for human ribosomopathies’, published in BiO. Sonu conducted the research described in this article while a PhD student in Patrick J. DiMario's lab at Louisiana State University, Baton Rouge, LA, USA. She is now a R&D scientist at Thermo Fisher Scientific, Santa Clara, CA, USA, investigating various genetic disorders relevant to reproductive health and newborn screening.

Nayeli G. Reyes-Nava, Hung-Chun Yu, Curtis R. Coughlin II, Tamim H. Shaikh, and Anita M. Quintana

We used whole-exome sequencing (WES) to determine the genetic etiology of a patient with a multi-system disorder characterized by a seizure phenotype. WES identified a heterozygous de novo missense mutation in the GABRA1 gene (c.875C>T). GABRA1 encodes the alpha subunit of the gamma-aminobutyric acid receptor A (GABA_AR). The GABA_AR is a ligand gated ion channel that mediates the fast inhibitory signals of the nervous system, and mutations in the subunits that compose the GABA_AR have been previously associated with human disease. To understand the mechanisms by which GABRA1 regulates brain development, we developed a zebrafish model of gabra1 deficiency. gabra1 expression is restricted to the nervous system and behavioral analysis of morpholino injected larvae suggests that the knockdown of gabra1 results in hypoactivity and defects in the expression of other subunits of the GABA_AR. Expression of the human GABRA1 protein in morphants partially restored the hypomotility phenotype. In contrast, the expression of the c.875C>T variant did not restore these behavioral deficits. Collectively, these results represent a functional approach to understand the mechanisms by which loss-of-function alleles cause disease.

BackgroundAutistic people are at increased risk of developing mental health problems. To reduce the negative impact of living with autism in a non-autistic world, efforts to improve take-up and access to care, and support in early years, which will typically start with a GP appointment, must be grounded in the accounts of autistic young adults.AimTo explore how autistic young adults understand and manage mental health problems; and to consider help seeking as a focus.Design and settingA cross-sectional, qualitative study. Autistic participants were purposively selected to represent a range of mental health conditions including anxiety and depression. A subsample were recruited from a population cohort screened for autism in childhood. The study concerns access to primary care.MethodNineteen autistic young adults without learning disabilities, aged 23 or 24 years, were recruited. In-depth, semi-structured interviews explored how they understood and managed mental health problems. Data were analysed thematically.ResultsYoung adults preferred self-management strategies. Multiple factors contributed to a focus on self-management, including: beliefs about the aetiology of mental health difficulties and increased vulnerability with the context of a diagnosis of autism, knowledge of self-management, and a view that formal support was unavailable or inadequate. Families had limited awareness of professional support.ConclusionYoung autistic adults without learning disabilities, and their families, may hold erroneous beliefs about autism and mental health. This may affect help seeking and contribute to an exacerbation of symptoms. GPs need to be alert to the fact that autistic young adults in their care may be experiencing mental health difficulties but may not recognise them as such.

BackgroundUrinary tract infections (UTIs) are one of the most common bacterial infections managed in general practice. Many women with symptoms of uncomplicated UTI may not benefit meaningfully from antibiotic treatment, but the evidence base is complex and there is no suitable shared decision-making resource to guide antibiotic treatment and symptomatic care for use in general practice consultations.AimTo develop an evidence-based, shared decision-making intervention leaflet to optimise management of uncomplicated UTI for women aged <65 years in the primary care setting.Design and settingQualitative telephone interviews with GPs and patient focus group interviews.MethodIn-depth interviews were conducted to explore how consultation discussions around diagnosis, antibiotic use, self-care, safety netting, and prevention of UTI could be improved. Interview schedules were based on the Theoretical Domains Framework.ResultsBarriers to an effective joint consultation and appropriate prescribing included: lack of GP time, misunderstanding of depth of knowledge and miscommunication between the patient and the GP, nature of the consults (such as telephone consultations), and a history of previous antibiotic therapy.ConclusionConsultation time pressures combined with late symptom presentation are a challenge for even the most experienced of GPs: however, it is clear that enhanced patient–clinician shared decision making is urgently required when it comes to UTIs. This communication should incorporate the provision of self-care, safety netting, and preventive advice to help guide patients when to consult. A shared decision-making information leaflet was iteratively co-produced with patients, clinicians, and researchers at Public Health England using study data.

Fnr is a transcriptional regulator that controls the expression of a variety of genes in response to oxygen limitation in bacteria. Genome sequencing revealed four genes (fnr1, fnr3, fnr5, and fnr7) coding for Fnr proteins in Paenibacillus polymyxa WLY78. Fnr1 and Fnr3 showed more similarity to each other than to Fnr5 and Fnr7. Also, Fnr1 and Fnr3 exhibited high similarity with Bacillus cereus Fnr and Bacillus subtilis Fnr in sequence and structures. Both the aerobically purified His-tagged Fnr1 and His-tagged Fnr3 in Escherichia coli could bind to the specific DNA promoter. Deletion analysis showed that the four fnr genes, especially fnr1 and fnr3, have significant impacts on growth and nitrogenase activity. Single deletion of fnr1 or fnr3 led to a 50% reduction in nitrogenase activity, and double deletion of fnr1 and fnr3 resulted to a 90% reduction in activity. Genome-wide transcription analysis showed that Fnr1 and Fnr3 indirectly activated expression of nif (nitrogen fixation) genes and Fe transport genes under anaerobic conditions. Fnr1 and Fnr3 inhibited expression of the genes involved in the aerobic respiratory chain and activated expression of genes responsible for anaerobic electron acceptor genes.

IMPORTANCE The members of the nitrogen-fixing Paenibacillus spp. have great potential to be used as a bacterial fertilizer in agriculture. However, the functions of the fnr gene(s) in nitrogen fixation and other metabolisms in Paenibacillus spp. are not known. Here, we found that in P. polymyxa WLY78, Fnr1 and Fnr3 were responsible for regulation of numerous genes in response to changes in oxygen levels, but Fnr5 and Fnr7 exhibited little effect. Fnr1 and Fnr3 indirectly or directly regulated many types of important metabolism, such as nitrogen fixation, Fe uptake, respiration, and electron transport. This study not only reveals the function of the fnr genes of P. polymyxa WLY78 in nitrogen fixation and other metabolisms but also will provide insight into the evolution and regulatory mechanisms of fnr in Paenibacillus.

This study investigated the effects of long-term soil fertilization on the composition and potential for phosphorus (P) and nitrogen (N) cycling of bacterial communities associated with hyphae of the P-solubilizing fungus Penicillium canescens. Using a baiting approach, hyphosphere bacterial communities were recovered from three soils that had received long-term amendment in the field with mineral or mineral plus organic fertilizers. P. canescens hyphae recruited bacterial communities with a decreased diversity and an increased abundance of Proteobacteria relative to what was observed in soil communities. As core bacterial taxa, Delftia and Pseudomonas spp. were present in all hyphosphere samples irrespective of soil fertilization. However, the type of fertilization showed significant impacts on the diversity, composition, and distinctive taxa/operational taxonomic units (OTUs) of hyphosphere communities. The soil factors P (Olsen method), exchangeable Mg, exchangeable K, and pH were important for shaping soil and hyphosphere bacterial community compositions. An increased relative abundance of organic P metabolism genes was found in hyphosphere communities from soil that had not received P fertilizers, which could indicate P limitation near the fungal hyphae. Additionally, P. canescens hyphae recruited bacterial communities with a higher abundance of N fixation genes than found in soil communities, which might imply a role of hyphosphere communities for fungal N nutrition. Furthermore, the relative abundances of denitrification genes were greater in several hyphosphere communities, indicating an at least partly anoxic microenvironment with a high carbon-to-N ratio around the hyphae. In conclusion, soil fertilization legacy shapes P. canescens hyphosphere microbiomes and their functional potential related to P and N cycling.

IMPORTANCE P-solubilizing Penicillium strains are introduced as biofertilizers to agricultural soils to improve plant P nutrition. Currently, little is known about the ecology of these biofertilizers, including their interactions with other soil microorganisms. This study shows that communities dominated by Betaproteobacteria and Gammaproteobacteria colonize P. canescens hyphae in soil and that the compositions of these communities depend on the soil conditions. The potential of these communities for N and organic P cycling is generally higher than that of soil communities. The high potential for organic P metabolism might complement the ability of the fungus to solubilize inorganic P, and it points to the hyphosphere as a hot spot for P metabolism. Furthermore, the high potential for N fixation could indicate that P. canescens recruits bacteria that are able to improve its N nutrition. Hence, this community study identifies functional groups relevant for the future optimization of next-generation biofertilizer consortia for applications in soil.

Resistance to the "last-resort" antibiotics, such as carbapenems, has led to very few antibiotics being left to treat infections by multidrug-resistant bacteria. Spread of carbapenem resistance (CR) has been well characterized for the clinical environment. However, there is a lack of information about its environmental distribution. Our study reveals that CR is present in a wide range of Gram-negative bacteria in the coastal seawater environment, including four phyla, eight classes, and 30 genera. These bacteria were likely introduced into seawater via stormwater flows. Some CR isolates found here, such as Acinetobacter junii, Acinetobacter johnsonii, Brevundimonas vesicularis, Enterococcus durans, Pseudomonas monteilii, Pseudomonas fulva, and Stenotrophomonas maltophilia, are further relevant to human health. We also describe a novel metallo-β-lactamase (MBL) for marine Rheinheimera isolates with CR, which has likely been horizontally transferred to Citrobacter freundii or Enterobacter cloacae. In contrast, another MBL of the New Delhi type was likely acquired by environmental Variovorax isolates from Escherichia coli, Klebsiella pneumoniae, or Acinetobacter baumannii utilizing a plasmid. Our findings add to the growing body of evidence that the aquatic environment is both a reservoir and a vector for novel CR genes.

IMPORTANCE Resistance against the "last-resort" antibiotics of the carbapenem family is often based on the production of carbapenemases, and this has been frequently observed in clinical samples. However, the dissemination of carbapenem resistance (CR) in the environment has been less well explored. Our study shows that CR is commonly found in a range of bacterial taxa in the coastal aquatic environment and can involve the exchange of novel metallo-β-lactamases from typical environmental bacteria to potential human pathogens or vice versa. The outcomes of this study contribute to a better understanding of how aquatic and marine bacteria can act as reservoirs and vectors for CR outside the clinical setting.

Random transposon mutagenesis is a powerful and unbiased genetic approach to answer fundamental biological questions. Here, we introduce an improved mariner-based transposon system with enhanced stability during propagation and versatile applications in mutagenesis. We used a low-copy-number plasmid as a transposon delivery vehicle, which affords a lower frequency of unintended recombination during vector construction and propagation in Escherichia coli. We generated a variety of transposons allowing for gene disruption or artificial overexpression, each in combination with one of four different antibiotic resistance markers. In addition, we provide transposons that will report gene/protein expression due to transcriptional or translational coupling. We believe that the TnFLX system will help enhance the flexibility of future transposon modification and application in Bacillus and other organisms.

IMPORTANCE The stability of transposase-encoding vectors during cloning and propagation is crucial for the reliable application of transposons. Here, we increased the stability of the mariner delivery vehicle in E. coli. Moreover, the TnFLX transposon system will improve the application of forward genetic methods with an increased number of antibiotic resistance markers and the ability to generate unbiased green fluorescent protein (GFP) fusions to report on protein translation and subcellular localization.

Dietary protein residue can result in microbial generation of various toxic metabolites in the gut, such as ammonia. A prebiotic is "a substrate that is selectively utilised by host microorganisms conferring a health benefit" (G. R. Gibson, R. Hutkins, M. E. Sanders, S. L. Prescott, et al., Nat Rev Gastroenterol Hepatol 14:491–502, 2017, https://doi.org/10.1038/nrgastro.2017.75). Prebiotics are carbohydrates that may have the potential to reverse the harmful effects of gut bacterial protein fermentation. Three-stage continuous colonic model systems were inoculated with fecal samples from omnivore and vegetarian volunteers. Casein (equivalent to 105 g protein consumption per day) was used within the systems as a protein source. Two different doses of inulin-type fructans (Synergy1) were later added (equivalent to 10 g per day in vivo and 15 g per day) to assess whether this influenced protein fermentation. Bacteria were enumerated by fluorescence in situ hybridization with flow cytometry. Metabolites from bacterial fermentation (short-chain fatty acid [SCFA], ammonia, phenol, indole, and p-cresol) were monitored to further analyze proteolysis and the prebiotic effect. A significantly higher number of bifidobacteria was observed with the addition of inulin together with reduction of Desulfovibrio spp. Furthermore, metabolites from protein fermentation, such as branched-chain fatty acids (BCFA) and ammonia, were significantly lowered with Synergy1. Production of p-cresol varied among donors, as we recognized four high producing models and two low producing models. Prebiotic addition reduced its production only in vegetarian high p-cresol producers.

IMPORTANCE Dietary protein levels are generally higher in Western populations than in the world average. We challenged three-stage continuous colonic model systems containing high protein levels and confirmed the production of potentially harmful metabolites from proteolysis, especially replicates of the transverse and distal colon. Fermentations of proteins with a prebiotic supplementation resulted in a change in the human gut microbiota and inhibited the production of some proteolytic metabolites. Moreover, we observed both bacterial and metabolic differences between fecal bacteria from omnivore donors and vegetarian donors. Proteins with prebiotic supplementation showed higher Bacteroides spp. and inhibited Clostridium cluster IX in omnivore models, while in vegetarian modes, Clostridium cluster IX was higher and Bacteroides spp. lower with high protein plus prebiotic supplementation. Synergy1 addition inhibited p-cresol production in vegetarian high p-cresol-producing models while the inhibitory effect was not seen in omnivore models.

A longstanding awareness in generating resistance to common antimicrobial therapies by Gram-negative bacteria has made them a major threat to global health. The application of antimicrobial peptides as a therapeutic agent would be a great opportunity to combat bacterial diseases. Here, we introduce a new antimicrobial peptide (~8.3 kDa) from probiotic strain Lactobacillus acidophilus ATCC 4356, designated acidocin 4356 (ACD). This multifunctional peptide exerts its anti-infective ability against Pseudomonas aeruginosa through an inhibitory action on virulence factors, bacterial killing, and biofilm degradation. Reliable performance over tough physiological conditions and low hemolytic activity confirmed a new hope for the therapeutic setting. Antibacterial kinetic studies using flow cytometry technique showed that the ACD activity is related to the change in permeability of the membrane. The results obtained from molecular dynamic (MD) simulation were perfectly suited to the experimental data of ACD behavior. The structure-function relationship of this natural compound, along with the results of transmission electron microscopy analysis and MD simulation, confirmed the ability of the ACD aimed at enhancing bacterial membrane perturbation. The peptide was effective in the treatment of P. aeruginosa infection in mouse model. The results support the therapeutic potential of ACD for the treatment of Pseudomonas infections.

IMPORTANCE Multidrug-resistant bacteria are a major threat to global health, and the Pseudomonas bacterium with the ability to form biofilms is considered one of the main causative agents of nosocomial infections. Traditional antibiotics have failed because of increased resistance. Thus, finding new biocompatible antibacterial drugs is essential. Antimicrobial peptides are produced by various organisms as a natural defense mechanism against pathogens, inspiring the possible design of the next generation of antibiotics. In this study, a new antimicrobial peptide was isolated from Lactobacillus acidophilus ATCC 4356, counteracting both biofilm and planktonic cells of Pseudomonas aeruginosa. A detailed investigation was then conducted concerning the functional mechanism of this peptide by using fluorescence techniques, electron microscopy, and in silico methods. The antibacterial and antibiofilm properties of this peptide may be important in the treatment of Pseudomonas infections.

In Lysobacter enzymogenes OH11, RpfB1 and RpfB2 were predicted to encode acyl coenzyme A (CoA) ligases. RpfB1 is located in the Rpf gene cluster. Interestingly, we found an RpfB1 homolog (RpfB2) outside this canonical gene cluster, and nothing is known about its functionality or mechanism. Here, we report that rpfB1 and rpfB2 can functionally replace EcFadD in the Escherichia coli fadD mutant JW1794. RpfB activates long-chain fatty acids (n-C_16:0 and n-C_18:0) for the corresponding fatty acyl-CoA ligase (FCL) activity in vitro, and Glu-361 plays critical roles in the catalytic mechanism of RpfB1 and RpfB2. Deletion of rpfB1 and rpfB2 resulted in significantly increased heat-stable antifungal factor (HSAF) production, and overexpression of rpfB1 or rpfB2 completely suppressed HSAF production. Deletion of rpfB1 and rpfB2 resulted in increased L. enzymogenes diffusible signaling factor 3 (LeDSF3) synthesis in L. enzymogenes. Overall, our results showed that changes in intracellular free fatty acid levels significantly altered HSAF production. Our report shows that intracellular free fatty acids are required for HSAF production and that RpfB affects HSAF production via FCL activity. The global transcriptional regulator Clp directly regulated the expression of rpfB1 and rpfB2. In conclusion, these findings reveal new roles of RpfB in antibiotic biosynthesis in L. enzymogenes.

IMPORTANCE Understanding the biosynthetic and regulatory mechanisms of heat-stable antifungal factor (HSAF) could improve the yield in Lysobacter enzymogenes. Here, we report that RpfB1 and RpfB2 encode acyl coenzyme A (CoA) ligases. Our research shows that RpfB1 and RpfB2 affect free fatty acid metabolism via fatty acyl-CoA ligase (FCL) activity to reduce the substrate for HSAF synthesis and, thereby, block HSAF production in L. enzymogenes. Furthermore, these findings reveal new roles for the fatty acyl-CoA ligases RpfB1 and RpfB2 in antibiotic biosynthesis in L. enzymogenes. Importantly, the novelty of this work is the finding that RpfB2 lies outside the Rpf gene cluster and plays a key role in HSAF production, which has not been reported in other diffusible signaling factor (DSF)/Rpf-producing bacteria.

Bacteria accumulate small, organic compounds called compatible solutes via uptake from the environment or biosynthesis from available precursors to maintain the turgor pressure of the cell in response to osmotic stress. The halophile Vibrio parahaemolyticus has biosynthesis pathways for the compatible solutes ectoine (encoded by ectABC-asp_ect) and glycine betaine (encoded by betIBA-proXWV), four betaine-carnitine-choline transporters (encoded by bccT1 to bccT4), and a second ProU transporter (encoded by proVWX). All of these systems are osmotically inducible with the exception of bccT2. Previously, it was shown that CosR, a MarR-type regulator, was a direct repressor of ectABC-asp_ect in Vibrio species. In this study, we investigated whether CosR has a broader role in the osmotic stress response. Expression analyses demonstrated that betIBA-proXWV, bccT1, bccT3, bccT4, and proVWX are repressed in low salinity. Examination of an in-frame cosR deletion mutant showed that expression of these systems is derepressed in the mutant at low salinity compared with the wild type. DNA binding assays demonstrated that purified CosR binds directly to the regulatory region of both biosynthesis systems and four transporters. In Escherichia coli green fluorescent protein (GFP) reporter assays, we demonstrated that CosR directly represses transcription of betIBA-proXWV, bccT3, and proVWX. Similar to Vibrio harveyi, we showed betIBA-proXWV was directly activated by the quorum-sensing LuxR homolog OpaR, suggesting a conserved mechanism of regulation among Vibrio species. Phylogenetic analysis demonstrated that CosR is ancestral to the Vibrionaceae family, and bioinformatics analysis showed widespread distribution among Gammaproteobacteria in general. Incidentally, in Aliivibrio fischeri, Aliivibrio finisterrensis, Aliivibrio sifiae, and Aliivibrio wodanis, an unrelated MarR-type regulator gene named ectR was clustered with ectABC-asp, which suggests the presence of another novel ectoine biosynthesis regulator. Overall, these data show that CosR is a global regulator of osmotic stress response that is widespread among bacteria.

IMPORTANCE Vibrio parahaemolyticus can accumulate compatible solutes via biosynthesis and transport, which allow the cell to survive in high salinity conditions. There is little need for compatible solutes under low salinity conditions, and biosynthesis and transporter systems need to be repressed. However, the mechanism(s) of this repression is not known. In this study, we showed that CosR played a major role in the regulation of multiple compatible solute systems. Phylogenetic analysis showed that CosR is present in all members of the Vibrionaceae family as well as numerous Gammaproteobacteria. Collectively, these data establish CosR as a global regulator of the osmotic stress response that is widespread in bacteria, controlling many more systems than previously demonstrated.

The response to iron limitation of the Gram-positive soil bacterium Corynebacterium glutamicum was analyzed with respect to secreted metabolites, the transcriptome, and the proteome. During growth in glucose minimal medium, iron limitation caused a shift from lactate to pyruvate as the major secreted organic acid complemented by l-alanine and 2-oxoglutarate. Transcriptome and proteome analyses revealed that a pronounced iron starvation response governed by the transcriptional regulators DtxR and RipA was detectable in the late, but not in the early, exponential-growth phase. A link between iron starvation and thiamine pyrophosphate (TPP) biosynthesis was uncovered by the strong upregulation of thiC. As phosphomethylpyrimidine synthase (ThiC) contains an iron-sulfur cluster, limiting activities of the TPP-dependent pyruvate–2-oxoglutarate dehydrogenase supercomplex probably cause the excretion of pyruvate and 2-oxoglutarate. In line with this explanation, thiamine supplementation could strongly diminish the secretion of these acids. The upregulation of thiC and other genes involved in thiamine biosynthesis and transport is presumably due to TPP riboswitches present at the 5' end of the corresponding operons. The results obtained in this study provide new insights into iron homeostasis in C. glutamicum and demonstrate that the metabolic consequences of iron limitation can be due to the iron dependency of coenzyme biosynthesis.

IMPORTANCE Iron is an essential element for most organisms but causes problems due to poor solubility under oxic conditions and due to toxicity by catalyzing the formation of reactive oxygen species (ROS). Therefore, bacteria have evolved complex regulatory networks for iron homeostasis aiming at a sufficient iron supply while minimizing ROS formation. In our study, the responses of the actinobacterium Corynebacterium glutamicum to iron limitation were analyzed, resulting in a detailed view on the processes involved in iron homeostasis in this model organism. In particular, we provide evidence that iron limitation causes TPP deficiency, presumably due to insufficient activity of the iron-dependent phosphomethylpyrimidine synthase (ThiC). TPP deficiency was deduced from the upregulation of genes controlled by a TPP riboswitch and secretion of metabolites caused by insufficient activity of the TPP-dependent enzymes pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. To our knowledge, the link between iron starvation and thiamine synthesis has not been elaborated previously.

Background:

It is unclear how patient-reported access to primary care differs by physician payment model and participation in team-based care. We examined the association between timely and after-hours access to primary care and physician payment model and participation in team-based care, and sought to assess how access varied by patient characteristics.

Methods:

We conducted a cross-sectional analysis of adult (age ≥ 16 yr) Ontarians who responded to the Ontario Health Care Experience Survey between January 2013 and September 2015, reported having a primary care provider and agreed to have their responses linked to health administrative data. Access measures included the proportion of respondents who reported same-day or next-day access when sick, satisfaction with time to appointment when sick, telephone access and knowledge of an after-hours clinic. We tested the association between practice model and measures of access using logistic regression after stratifying for rurality.

Results:

A total of 33 665 respondents met our inclusion criteria. In big cities, respondents in team and nonteam capitation models were less likely to report same-day or next-day access when sick than respondents in enhanced fee-for-service models (team capitation 43%, adjusted odds ratio [OR] 0.88, 95% confidence interval [CI] 0.79–0.98; nonteam capitation 39%, adjusted OR 0.78, 95% CI 0.70–0.87; enhanced fee-for-service 46% [reference]). Respondents in team and nonteam capitation models were more likely than those in enhanced fee-for-service models to report that their provider had an after-hours clinic (team capitation 59%, adjusted OR 2.59, 95% CI 2.39–2.81; nonteam capitation 51%, adjusted OR 1.90, 95% CI 1.76–2.04; enhanced fee-for service 34% [reference]). Patterns were similar for respondents in small towns. There was minimal to no difference by model for satisfaction with time to appointment or telephone access.

Interpretation:

In our setting, there was an association between some types of access to primary care and physician payment model and team-based care, but the direction was not consistent. Different measures of timely access are needed to understand health care system performance.

Background:

First Nations people in Ontario have an increased prevalence of diabetes compared to other people in the province. This study examined use of health care services by First Nations people with diabetes and other people with diabetes in Ontario.

Methods:

Using linked health administrative databases, we identified all people in Ontario with diabetes as of Apr. 1, 2014. We identified First Nations people using the Indian Register. We looked at outcomes from Apr. 1, 2014, to Mar. 31, 2015. We determined the proportion of people with a regular family physician and their continuity of care with that physician. We also examined visits with specialists for diabetes care, hospital admissions for ambulatory-care–sensitive conditions, and emergency department visits for hypo- or hyperglycemia.

Results:

There were 1 380 529 people diagnosed with diabetes in Ontario as of Apr. 1, 2014, of whom 22 952 (1.7%) were First Nations people. First Nations people were less likely to have a regular family physician (85.3% v. 97.7%) and had lower continuity of care with that physician (mean score for continuity of care 74.6 v. 77.7) than other people in Ontario. They were also less likely to see specialists. First Nations people were more likely to be admitted to hospital for ambulatory-care–sensitive conditions (2.4% v. 1.2%) and to have an emergency department visit for hypo- or hyperglycemia (1.5% v. 0.8%). Disparities were particularly marked for those living in First Nations communities.

Interpretation:

First Nations people with diabetes in Ontario had poorer access to and use of primary care than other people with diabetes in the province. These findings may help explain continued disparities in the rates of complications related to diabetes.

Background:

Peripregnancy emergency department use may be common, but data specific to health care systems like that in Canada are lacking. As prior research was limited to livebirths, omitting pregnancies ending in miscarriage or induced abortion, the current study quantified and characterized emergency department use among women in Ontario with a recognized pregnancy.

Methods:

This retrospective population-based cohort study included all recognized pregnancies among Ontario residents aged 10–55 years with an estimated date of conception between Apr. 1, 2002, and Mar. 31, 2017. We defined peripregnancy emergency department use as any emergency department visit during pregnancy or within 42 days after pregnancy. We used modified Poisson regression with a robust error variance to generate relative risks (RRs) and 95% confidence intervals (CIs) for the outcome of any peripregnancy emergency department use in association with maternal age, parity, residential income quintile, location of residence, immigrant status, antenatal care provider and number of comorbidities within 120 days before the clinical start of the pregnancy (expressed as total number of Aggregated Diagnosis Groups [ADGs] obtained with the Johns Hopkins Adjusted Clinical Group System). All RRs, except for number of comorbidities, were further adjusted for number of ADGs.

Results:

Peripregnancy emergency department use occurred in 1 075 991 (39.4%) of 2 728 236 recognized pregnancies, including 35.8% of livebirths, 47.3% of stillbirths, 73.7% of miscarriages and 84.8% of threatened abortions. A peripregnancy emergency department visit was more likely among women who were less than 25 years of age (adjusted RR 1.16, 95% CI 1.16–1.17), were nulliparous (adjusted RR 1.13, 95% CI 1.13–1.13), resided in the lowest income quintile area (adjusted RR 1.16, 95% CI 1.15–1.16) or in a rural area (adjusted RR 1.50, 95% CI 1.50–1.51), were Canadian-born (adjusted RR 1.22, 95% CI 1.22–1.23), were not seen by an obstetrician (adjusted RR 1.66, 95% CI 1.54–1.80) or had a greater number of ADGs. Emergency department use peaked in the first trimester and in the first week postpartum. Compared to women residing in urban areas, those residing in rural areas had an odds ratio (OR) of 3.44 (95% CI 3.39–3.49) for 3 or more emergency department visits. Women with 3–4 (OR 1.99, 95% CI 1.97–2.01), 5–6 (OR 3.55, 95% CI 3.49–3.61), or 7 or more (OR 7.59, 95% CI 7.39–7.78) prepregnancy comorbidities were more likely to have 3 or more peripregnancy emergency department visits than were those with 2 or fewer comorbidities.

Interpretation:

Peripregnancy emergency department use occurred in nearly 40% of pregnancies, notably in the first trimester and early in the postpartum period. Efforts are needed to streamline rapid access to ambulatory obstetric care during these peak periods, when women are susceptible to miscarriage or a complication after a livebirth.

Background:

In Canada, First Nations populations experience a higher incidence of diabetes and diabetes-related complications than other people. Given the paucity of information on use of preventive eye examinations and the need for interventional care for severe retinopathy among First Nations people, we carried out a population-based study to compare rates of eye examinations and interventional therapies to treat vision-threatening stages of diabetic retinopathy among First Nations people and other people with diabetes in Ontario.

Methods:

In collaboration with the Chiefs of Ontario, we carried out a population-based study to identify cohorts of First Nations people and other people with diabetes in Ontario from 1995/96 to 2014/15. We used linked health administrative databases to evaluate rates of eye examination (2005/06–2014/15) and severe diabetic retinopathy treatment and compared them between the 2 populations, and between First Nations people living in and outside of First Nations communities.

Results:

We identified 23 013 First Nations people and 1 364 222 other people diagnosed with diabetes from 1995/96 to 2014/15, of whom 49.8% (95% confidence interval [CI] 48.9%–50.7%) and 53.8% (95% CI 53.7%–54.0%), respectively, received an eye examination in 2014/15. Eye examination rates were similar for First Nations people regardless of whether they lived in or outside a First Nations community. First Nations people developed severe diabetic retinopathy at a faster rate than other people (hazard ratio 1.19, 95% CI 1.02–1.38). The gap between First Nations people and other people in the proportion requiring therapy for severe diabetic retinopathy was especially prominent among younger people. There were no significant differences in rates of diabetic retinopathy treatment in First Nations people stratified by place of residence.

Interpretation:

Eye examination rates remain suboptimal among people with diabetes in Ontario and were lower among First Nations people. This is particularly concerning in light of our other findings showing an increased risk of requiring treatment for advanced diabetic retinopathy and the accelerated rate of diabetic retinopathy progression among First Nations people with diabetes.

Whether low plasma 25-hydroxyvitamin D concentrations cause osteoporotic fractures is unclear. We tested the hypothesis that low plasma 25-hydroxyvitamin D concentrations are associated with increased risk of osteoporotic fractures using a Mendelian randomization analysis.We genotyped 116 335 randomly chosen white Danish persons aged 20–100 years in 2 population-based cohort studies for plasma 25-hydroxyvitamin D decreasing genotypes in CYP2R1 (rs117913124 and rs12794714), DHCR7 (rs7944926 and rs11234027), GEMIN2 (rs2277458), and HAL (rs3819817); 35 833 had information on plasma 25-hydroxyvitamin D. We assessed risk of total, osteoporotic, and anatomically localized fractures from 1981 through 2017. Information on fractures and vital status was obtained from nationwide registries.During up to 36 years of follow-up, we observed 17 820 total fractures, 10 861 osteoporotic fractures, and 3472 fractures of hip or femur. Compared with individuals with 25-hydroxyvitamin D ≥ 50nmol/L, multivariable adjusted hazard ratios (95% CIs) for total fractures were 1.03 (0.97–1.09) for individuals with 25–49.9 nmol/L, 1.19 (1.10–1.28) for individuals with 12.5–24.9 nmol/L, and 1.39 (1.21–1.60) for individuals with 25-hydroxyvitamin D < 12.5 nmol/L. Corresponding hazard ratios were 1.07 (1.00–1.15), 1.25 (1.13–1.37), and 1.49 (1.25–1.77) for osteoporotic fractures and 1.09 (0.98–1.22), 1.37 (1.18–1.57), and 1.41 (1.09–1.81) for fractures of hip or femur, respectively. Hazard ratios per 1 increase in vitamin D allele score, corresponding to 3.0% (approximately 1.6 nmol/L) lower 25-hydroxyvitamin D concentrations, were 0.99 (0.98–1.00) for total fractures, 0.99 (0.97–1.00) for osteoporotic fractures, and 0.98 (0.95–1.00) for fractures of hip or femur.Low plasma 25-hydroxyvitamin D concentrations were associated with osteoporotic fractures; however, Mendelian randomization analysis provided no evidence supporting a causal role for vitamin D in the risk for osteoporotic fractures.

Caseum, the central necrotic material of tuberculous lesions, is a reservoir of drug-recalcitrant persisting mycobacteria. Caseum is found in closed nodules and in open cavities connecting with an airway. Several commonly accepted characteristics of caseum were established during the preantibiotic era, when autopsies of deceased tuberculosis (TB) patients were common but methodologies were limited. These pioneering studies generated concepts such as acidic pH, low oxygen tension, and paucity of nutrients being the drivers of nonreplication and persistence in caseum. Here we review widely accepted beliefs about the caseum-specific stress factors thought to trigger the shift of Mycobacterium tuberculosis to drug tolerance. Our current state of knowledge reveals that M. tuberculosis is faced with a lipid-rich diet rather than nutrient deprivation in caseum. Variable caseum pH is seen across lesions, possibly transiently acidic in young lesions but overall near neutral in most mature lesions. Oxygen tension is low in the avascular caseum of closed nodules and high at the cavity surface, and a gradient of decreasing oxygen tension likely forms toward the cavity wall. Since caseum is largely made of infected and necrotized macrophages filled with lipid droplets, the microenvironmental conditions encountered by M. tuberculosis in foamy macrophages and in caseum bear many similarities. While there remain a few knowledge gaps, these findings constitute a solid starting point to develop high-throughput drug discovery assays that combine the right balance of oxygen tension, pH, lipid abundance, and lipid species to model the profound drug tolerance of M. tuberculosis in caseum.

Burkholderia cepacia (formerly Pseudomonas cepacia) was once thought to be a single bacterial species but has expanded to the Burkholderia cepacia complex (Bcc), comprising 24 closely related opportunistic pathogenic species. These bacteria have a widespread environmental distribution, an extraordinary metabolic versatility, a complex genome with three chromosomes, and a high capacity for rapid mutation and adaptation. Additionally, they present an inherent resistance to antibiotics and antiseptics, as well as the abilities to survive under nutrient-limited conditions and to metabolize the organic matter present in oligotrophic aquatic environments, even using certain antimicrobials as carbon sources. These traits constitute the reason that Bcc bacteria are considered feared contaminants of aqueous pharmaceutical and personal care products and the frequent reason behind nonsterile product recalls. Contamination with Bcc has caused numerous nosocomial outbreaks in health care facilities, presenting a health threat, particularly for patients with cystic fibrosis and chronic granulomatous disease and for immunocompromised individuals. This review addresses the role of Bcc bacteria as a potential public health problem, the mechanisms behind their success as contaminants of pharmaceutical products, particularly in the presence of biocides, the difficulties encountered in their detection, and the preventive measures applied during manufacturing processes to control contamination with these objectionable microorganisms. A summary of Bcc-related outbreaks in different clinical settings, due to contamination of diverse types of pharmaceutical products, is provided.

Intrathecal administration of anti-infectives is indicated in central nervous system infections by multiresistant pathogens when drugs that can reach adequate cerebrospinal fluid (CSF) concentrations by systemic therapy are not available. Antibiotics that readily pass the blood-brain and blood-CSF barriers and/or that have low toxicity allowing an increase in the daily dosage should not be used for intrathecal therapy. Intrathecal therapy is accompanied by systemic treatment. Antibacterials indispensable for intrathecal therapy include aminoglycosides, colistin, daptomycin, tigecycline, and vancomycin. Limited experience suggests the utility of the antifungals amphotericin B and caspofungin. Intraventricular administration ensures distribution throughout the CSF compartment, whereas intralumbar dosing often fails to attain adequate antibiotic concentrations in the ventricles. The individual dose is determined by the estimated size of the CSF space and by the estimated clearance from CSF. For moderately lipophilic anti-infectives with a molecular weight above approximately 1,000 g/mol, as well as for hydrophilic drugs with a molecular weight above approximately 400 g/mol, one daily dose is normally adequate. The ventricular drain should be clamped for 15 to 120 min to facilitate the distribution of the anti-infective in the CSF space. Therapeutic drug monitoring of the trough levels is necessary only in cases of therapeutic failure.

Purpose:

Human B7-H3 (hB7-H3) is a promising molecular imaging target differentially expressed on the neovasculature of breast cancer and has been validated for preclinical ultrasound (US) imaging with anti–B7-H3-antibody-functionalized microbubbles (MB). However, smaller ligands such as affibodies (ABY) are more suitable for the design of clinical-grade targeted MB.

Experimental Design:

Binding of ABY_B7-H3 was confirmed with soluble and cell-surface B7-H3 by flow cytometry. MB were functionalized with ABY_B7-H3 or anti–B7-H3-antibody (Ab_B7-H3). Control and targeted MB were tested for binding to hB7-H3–expressing cells (MS1_hB7-H3) under shear stress conditions. US imaging was performed with MB_ABY-B7-H3 in an orthotopic mouse model of human MDA-MB-231 coimplanted with MS1_hB7-H3 or control MS1_WT cells and a transgenic mouse model of breast cancer development.

Results:

ABY_B7-H3 specifically binds to MS1_hB7-H3 and murine-B7-H3–expressing monocytes. MB_ABY-B7-H3 (8.5 ± 1.4 MB/cell) and MB_Ab-B7-H3 (9.8 ± 1.3 MB/cell) showed significantly higher (P < 0.0001) binding to the MS1_hB7-H3 cells compared with control MB_Non-targeted (0.5 ± 0.1 MB/cell) under shear stress conditions. In vivo, MB_ABY-B7-H3 produced significantly higher (P < 0.04) imaging signal in orthotopic tumors coengrafted with MS1_hB7-H3 (8.4 ± 3.3 a.u.) compared with tumors with MS1_WT cells (1.4 ± 1.0 a.u.). In the transgenic mouse tumors, MB_ABY-B7-H3 (9.6 ± 2.0 a.u.) produced higher (P < 0.0002) imaging signal compared with MB_Non-targeted (1.3 ± 0.3 a.u.), whereas MB_ABY-B7-H3 signal in normal mammary glands and tumors with B7-H3 blocking significantly reduced (P < 0.02) imaging signal.

Conclusions:

MB_ABY-B7-H3 enhances B7-H3 molecular signal in breast tumors, improving cancer detection, while offering the advantages of a small size ligand and easier production for clinical imaging.

The impact on survival of steroids and TNFα blockade to treat immune-related toxicity from checkpoint blockade with ipilimumab, nivolumab/pembrolizumab, or combined ipilimumab and nivolumab was assessed using data from a large national database. Using steroids was associated with better survival than the use of TNFα-blocking antibodies such as infliximab.

See related article by Verheijden et al., p. 2268

In this retrospective study, whole-genome sequencing (WGS) data generated on an Ion Torrent platform was used to predict phenotypic drug resistance profiles for first- and second-line drugs among Swedish clinical Mycobacterium tuberculosis isolates from 2016 to 2018. The accuracy was ~99% for all first-line drugs and 100% for four second-line drugs. Our analysis supports the introduction of WGS into routine diagnostics, which might, at least in Sweden, replace phenotypic drug susceptibility testing in the future.

New drugs or therapeutic combinations are urgently needed against Mycobacterium abscessus. Previously, we demonstrated the potent activity of indole-2-carboxamides 6 and 12 against M. abscessus. We show here that these compounds act synergistically with imipenem and cefoxitin in vitro and increase the bactericidal activity of the β-lactams against M. abscessus. In addition, compound 12 also displays synergism with imipenem and cefoxitin within infected macrophages. The clinical potential of these new drug combinations requires further evaluation.

Tigecycline serves as one of the antibiotics of last resort to treat multidrug-resistant (including carbapenem-resistant) pathogens. However, the recently emerged plasmid-mediated tigecycline resistance mechanism, Tet(X), challenges the clinical efficacy of this class of antibiotics. In this study, we detected 180 tet(X)-harboring Acinetobacter isolates (8.9%, n = 180) from 2,018 samples collected from avian farms and adjacent environments in China. Eighteen tet(X)-harboring isolates (10.0%) were found to cocarry the carbapenemase gene bla_NDM-1, mostly from waterfowl samples (94.4%, 17/18). Interestingly, among six Acinetobacter strains, tet(X) and bla_NDM-1 were found to colocalize on the same plasmids. Moreover, whole-genome sequencing (WGS) revealed a novel orthologue of tet(X) in the six isolates coharboring tet(X) and bla_NDM-1. Inverse PCR suggested that the two tet(X) genes form a single transposable unit and may be cotransferred. Sequence comparison between six tet(X)- and bla_NDM-1-coharboring plasmids showed that they shared a highly homologous plasmid backbone even though they were isolated from different Acinetobacter species (three from Acinetobacter indicus, two from Acinetobacter schindleri, and one from Acinetobacter lwoffii) from various sources and from different geological regions, suggesting the horizontal genetic transfer of a common tet(X)- and bla_NDM-1-coharboring plasmid among Acinetobacter species in China. Emergence and spread of such plasmids and strains are of great clinical concern, and measures must be implemented to avoid their dissemination.

Plazomicin was active against 97.0% of 8,783 Enterobacterales isolates collected in the United States (2016 and 2017), and only 6 isolates carried 16S rRNA methyltransferases conferring resistance to virtually all aminoglycosides. Plazomicin (89.2% to 95.9% susceptible) displayed greater activity than amikacin (72.5% to 78.6%), gentamicin (30.4% to 45.9%), and tobramycin (7.8% to 22.4%) against carbapenem-resistant and extensively drug-resistant isolates. The discrepancies among the susceptibility rates for these agents was greater when applying breakpoints generated using the same stringent contemporary methods applied to determine plazomicin breakpoints.

Imipenem-relebactam (I-R) is a recently developed carbapenem–beta-lactamase inhibitor combination agent that can overcome carbapenem resistance, which has now emerged in Escherichia coli, including sequence type 131 (ST131) and its fluoroquinolone-resistant H30R subclone, the leading cause of extraintestinal E. coli infections globally. To clarify the likely utility of I-R for carbapenem-resistant (CR) E. coli infections in the United States, we characterized 203 recent CR clinical E. coli isolates from across the United States (years 2002 to 2017) for phylogroup, clonal group (including ST131, H30R, and the CTX-M-15-associated H30Rx subset within H30R), relevant beta-lactamase genes, and broth microdilution MICs for I-R and 11 comparator agents. Overall, I-R was highly active (89% susceptible), more so than all comparators except tigecycline and colistin (both 99% susceptible). I-R’s activity varied significantly in relation to phylogroup, clonal background, resistance genotype, and region. It was greatest among phylogroup B2, ST131-H30R, H30Rx, Klebsiella pneumoniae carbapenemase (KPC)-positive, and northeast U.S. isolates and lowest among phylogroup C, New Delhi metallo-β-lactamase (NDM)-positive, and southeast U.S. isolates. Relebactam improved imipenem’s activity against CR isolates within each phylogroup—especially groups A, B1, and B2—and particularly against isolates containing KPC. I-R remained substantially active against isolates coresistant to comparator agents, albeit somewhat less so than against the corresponding susceptible isolates. These findings suggest that I-R should be useful for treating most CR E. coli infections in the United States, largely independent of coresistance, although this likely will vary in relation to the local prevalence of specific E. coli lineages and carbapenem resistance mechanisms.

Bacterial persisters are phenotypic variants that temporarily demonstrate an extraordinary tolerance toward antibiotics. Persisters have been linked to the recalcitrance of biofilm-related infections; hence, a complete understanding of their physiology can lead to improvement of therapeutic strategies for such infections. Mechanisms pertaining to persister formation are thought to be associated with stress response pathways triggered by intra- or extracellular stress factors. Unfortunately, studies demonstrating the effects of osmolyte- and/or pH-induced stresses on bacterial persistence are largely missing. To fill this knowledge gap within the field, we studied the effects of various osmolytes and pH conditions on Escherichia coli persistence with the use of phenotype microarrays and antibiotic tolerance assays. Although we found that a number of chemicals and pH environments, including urea, sodium nitrite, and acidic pH, significantly reduced persister formation in E. coli compared to no-osmolyte/no-buffer controls, this reduction in persister levels was less pronounced in late-stationary-phase cultures. Our results further demonstrated a positive correlation between cell growth and persister formation, which challenges the general notion in the field that slow-growing cultures have more persister cells than fast-growing cultures.

KBP-7072 is a novel third-generation tetracycline (aminomethylcycline) antibacterial that overcomes common efflux and ribosomal protection resistance mechanisms that cause resistance in older-generation tetracyclines. KBP-7072 completed phase 1 clinical development studies for safety, tolerability, and pharmacokinetics (ClinicalTrials.gov identifier NCT02454361) and multiple ascending doses in healthy subjects (ClinicalTrials.gov identifier NCT02654626) in December 2015. Both oral and intravenous formulations of KBP-7072 are being developed. In this study, we evaluated the in vitro activities of KBP-7072 and comparator agents by CLSI document M07 (2018) broth microdilution against 531 recent geographically diverse and/or molecularly characterized Acinetobacter baumannii-A. calcoaceticus species complex (A. baumannii) isolates from the United States, Europe, Asia-Pacific (excluding China), and Latin America. A. baumannii isolates included carbapenem-resistant, colistin-resistant, tetracycline-resistant, and extended-spectrum-β-lactamase (ESBL)- and metallo-β-lactamase (MBL)-producing isolates. Overall, KBP-7072 (MIC_50/90, 0.25/1 mg/liter) was comparable in activity to colistin (92.8%/92.8% susceptible [S] [CLSI/EUCAST]) against A. baumannii isolates, inhibiting 99.2% of isolates at ≤2 mg/liter and 97.6% of isolates at ≤1 mg/liter. KBP-7072 was equally active against A. baumannii isolates, including carbapenem-resistant, colistin-resistant, and tetracycline-resistant isolates, regardless of geographic location, and maintained activity against ESBL- and MBL-producing isolates. KBP-7072 outperformed comparator agents, including ceftazidime (40.3% S [CLSI]), gentamicin (48.2%/48.2% S [CLSI/EUCAST]), levofloxacin (39.5%/37.9% S [CLSI/EUCAST]), meropenem (42.0%/42.0% S [CLSI/EUCAST]), piperacillin-tazobactam (33.3% S [CLSI]), and all tetracycline-class comparator agents, which include doxycycline (67.3% S [CLSI]), minocycline (73.8% S [CLSI]), tetracycline (37.2% S [CLSI]), and tigecycline (79.5% inhibited by ≤2 mg/liter). The potent in vitro activity of KBP-7072 against recent geographically diverse, molecularly characterized, and drug-resistant A. baumannii isolates supports continued clinical development for the treatment of serious infections, including those caused by A. baumannii.

Nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP), is increasingly associated with multidrug-resistant Gram-negative pathogens. This study describes the in vitro activity of ceftazidime-avibactam, ceftazidime, and relevant comparator agents against bacterial pathogens isolated from patients with NP, including VAP, enrolled in a ceftazidime-avibactam phase 3 trial. Gram-positive pathogens were included if coisolated with a Gram-negative pathogen. In vitro susceptibility was determined at a central laboratory using Clinical and Laboratory Standards Institute broth microdilution methods. Of 817 randomized patients, 457 (55.9%) had ≥1 Gram-negative bacterial pathogen(s) isolated at baseline, and 149 (18.2%) had ≥1 Gram-positive pathogen(s) coisolated. The most common isolated pathogens were Klebsiella pneumoniae (18.8%), Pseudomonas aeruginosa (15.8%), and Staphylococcus aureus (11.5%). Ceftazidime-avibactam was highly active in vitro against 370 isolates of Enterobacteriaceae, with 98.6% susceptible (MIC₉₀, 0.5 μg/ml) compared with 73.2% susceptible for ceftazidime (MIC₉₀, >64 μg/ml). The percent susceptibility values for ceftazidime-avibactam and ceftazidime against 129 P. aeruginosa isolates were 88.4% and 72.9% (MIC₉₀ values of 16 μg/ml and 64 μg/ml), respectively. Among ceftazidime-nonsusceptible Gram-negative isolates, ceftazidime-avibactam percent susceptibility values were 94.9% for 99 Enterobacteriaceae and 60.0% for 35 P. aeruginosa. MIC₉₀ values for linezolid and vancomycin (permitted per protocol for Gram-positive coverage) were within their respective MIC susceptibility breakpoints against the Gram-positive pathogens isolated. This analysis demonstrates that ceftazidime-avibactam was active in vitro against the majority of Enterobacteriaceae and P. aeruginosa isolates from patients with NP, including VAP, in a phase 3 trial. (This study has been registered at ClinicalTrials.gov under identifier NCT01808092.)

Infections with nontuberculous mycobacteria (NTM) have a poor prognosis in patients with underlying respiratory diseases. Clofazimine (CFZ) showed both experimental and clinical promising results against clinically relevant NTM. However, there are no data on CFZ in combination with the current recommended treatment; therefore, we aimed to study its in vivo activity in an aerosol mouse model of Mycobacterium avium. In an aerosol infection BALB/c mouse model using M. avium strain Chester, we treated 58 mice with four combinations of rifampin (RIF) at 10 mg/kg, CFZ at 25 mg/kg, and clarithromycin (CLR) and ethambutol (EMB) at 100 mg/kg. Treatment efficacy was assessed on the basis of lung CFU counts after 2 (M2) and 4 (M4) months of treatment. At M2, CLR-RIF-EMB was slightly but significantly more efficient than CFZ-RIF-EMB (3.02 ± 0.12 versus 3.55 ± 0.28, respectively, P < 0.01), whereas CLR-CFZ-EMB and CLR-CFZ-RIF-EMB dramatically decreased lung CFU counts by 4.32 and 4.47 log₁₀, respectively, compared to untreated group. At M4, CLR-RIF-EMB was significantly more efficient than CFZ-RIF-EMB (2 ± 0.53 versus 2.66 ± 0.22, respectively, P = 0.01). The addition of CLZ to CLR dramatically decreased the lung CFU count, with CFU counts 5.41 and 5.79 log₁₀ lower in the CLR-CFZ-EMB and CLR-CFZ-RIF-EMB groups, respectively, than in the untreated group. The addition of CFZ to CLR seems to improve the efficacy of CLR as early as M2 and was confirmed at M4. CFZ, in addition to RIF and EMB, on the other hand, is less effective than CLR-RIF-EMB. These results need to be confirmed by similar studies along with CFZ potential for shortening treatment.

Antibiotics revolutionized the treatment of infectious diseases; however, it is now clear that broad-spectrum antibiotics alter the composition and function of the host’s microbiome. The microbiome plays a key role in human health, and its perturbation is increasingly recognized as contributing to many human diseases. Widespread broad-spectrum antibiotic use has also resulted in the emergence of multidrug-resistant pathogens, spurring the development of pathogen-specific strategies such as monoclonal antibodies (MAbs) to combat bacterial infection. Not only are pathogen-specific approaches not expected to induce resistance in nontargeted bacteria, but they are hypothesized to have minimal impact on the gut microbiome. Here, we compare the effects of antibiotics, pathogen-specific MAbs, and their controls (saline or control IgG [c-IgG]) on the gut microbiome of 7-week-old, female, C57BL/6 mice. The magnitude of change in taxonomic abundance, bacterial diversity, and bacterial metabolites, including short-chain fatty acids (SCFA) and bile acids in the fecal pellets from mice treated with pathogen-specific MAbs, was no different from that with animals treated with saline or an IgG control. Conversely, dramatic changes were observed in the relative abundance, as well as alpha and beta diversity, of the fecal microbiome and bacterial metabolites in the feces of all antibiotic-treated mice. Taken together, these results indicate that pathogen-specific MAbs do not alter the fecal microbiome like broad-spectrum antibiotics and may represent a safer, more-targeted approach to antibacterial therapy.

The comparative efficacy of ceftazidime-avibactam and meropenem-vaborbactam for treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections remains unknown. This was a multicenter, retrospective cohort study of adults with CRE infections who received ceftazidime-avibactam or meropenem-vaborbactam for ≥72 hours from February 2015 to October 2018. Patients with a localized urinary tract infection and repeat study drug exposures after the first episode were excluded. The primary endpoint was clinical success compared between treatment groups. Secondary endpoints included 30- and 90-day mortality, adverse events (AE), 90-day CRE infection recurrence, and development of resistance in patients with recurrent infection. A post hoc subgroup analysis was completed comparing patients who received ceftazidime-avibactam monotherapy, ceftazidime-avibactam combination therapy, and meropenem-vaborbactam monotherapy. A total of 131 patients were included (ceftazidime-avibactam, n = 105; meropenem-vaborbactam, n = 26), 40% of whom had bacteremia. No significant difference in clinical success was observed between groups (62% versus 69%; P = 0.49). Patients in the ceftazidime-avibactam arm received combination therapy more often than patients in the meropenem-vaborbactam arm (61% versus 15%; P < 0.01). No difference in 30- and 90-day mortality resulted, and rates of AE were similar between groups. In patients with recurrent infection, development of resistance occurred in three patients that received ceftazidime-avibactam monotherapy and in no patients in the meropenem-vaborbactam arm. Clinical success was similar between patients receiving ceftazidime-avibactam and meropenem-vaborbactam for treatment of CRE infections, despite ceftazidime-avibactam being used more often as a combination therapy. Development of resistance was more common with ceftazidime-avibactam monotherapy.

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung condition, causing progressive decline in lung function leading to premature death. Acute exacerbations in COPD patients are predominantly associated with respiratory viruses. Ribavirin is a generic broad-spectrum antiviral agent that could be used for treatment of viral respiratory infections in COPD. Using the Particle Replication In Nonwetting Templates (PRINT) technology, which produces dry-powder particles of uniform shape and size, two new inhaled formulations of ribavirin (ribavirin-PRINT-CFI and ribavirin-PRINT-IP) were developed for efficient delivery to the lung and to minimize bystander exposure. Ribavirin-PRINT-CFI was well tolerated in healthy participants after single dosing and ribavirin-PRINT-IP was well tolerated in healthy and COPD participants after single and repeat dosing. Ribavirin-PRINT-CFI was replaced with ribavirin-PRINT-IP since the latter formulation was found to have improved physicochemical properties and it had a higher ratio of active drug to excipient per unit dose. Ribavirin concentrations were measured in lung epithelial lining fluid in both healthy and COPD participants and achieved target concentrations. Both formulations were rapidly absorbed with approximately dose proportional pharmacokinetics in plasma. Exposure to bystanders was negligible based on both the plasma and airborne ribavirin concentrations with the ribavirin-PRINT-IP formulation. Thus, ribavirin-PRINT-IP allowed for an efficient and convenient delivery of ribavirin to the lungs while minimizing systemic exposure. Further clinical investigations would be required to demonstrate ribavirin-PRINT-IP antiviral characteristics and impact on COPD viral-induced exacerbations. (The clinical trials discussed in this study have been registered at ClinicalTrials.gov under identifiers NCT03243760 and NCT03235726.)

Carbapenem resistance in Enterobacterales is a public health threat. Klebsiella pneumoniae carbapenemase (encoded by alleles of the bla_KPC family) is one of the most common transmissible carbapenem resistance mechanisms worldwide. The dissemination of bla_KPC historically has been associated with distinct K. pneumoniae lineages (clonal group 258 [CG258]), a particular plasmid family (pKpQIL), and a composite transposon (Tn4401). In the United Kingdom, bla_KPC has represented a large-scale, persistent management challenge for some hospitals, particularly in North West England. The dissemination of bla_KPC has evolved to be polyclonal and polyspecies, but the genetic mechanisms underpinning this evolution have not been elucidated in detail; this study used short-read whole-genome sequencing of 604 bla_KPC-positive isolates (Illumina) and long-read assembly (PacBio)/polishing (Illumina) of 21 isolates for characterization. We observed the dissemination of bla_KPC (predominantly bla_KPC-2; 573/604 [95%] isolates) across eight species and more than 100 known sequence types. Although there was some variation at the transposon level (mostly Tn4401a, 584/604 [97%] isolates; predominantly with ATTGA-ATTGA target site duplications, 465/604 [77%] isolates), bla_KPC spread appears to have been supported by highly fluid, modular exchange of larger genetic segments among plasmid populations dominated by IncFIB (580/604 isolates), IncFII (545/604 isolates), and IncR (252/604 isolates) replicons. The subset of reconstructed plasmid sequences (21 isolates, 77 plasmids) also highlighted modular exchange among non-bla_KPC and bla_KPC plasmids and the common presence of multiple replicons within bla_KPC plasmid structures (>60%). The substantial genomic plasticity observed has important implications for our understanding of the epidemiology of transmissible carbapenem resistance in Enterobacterales for the implementation of adequate surveillance approaches and for control.

Animal models of bacterial infection have been widely used to explore the in vivo activity of antibacterial drugs. These data are often submitted to the U.S. Food and Drug Administration to support human use in an investigational new drug application (IND). To better understand the range and scientific use of animal models in regulatory submissions, a database was created surveying recent pneumonia models submitted as part of IND application packages. The IND studies were compared to animal models of bacterial pneumonia published in the scientific literature over the same period of time. In this review, we analyze the key experimental design elements, such as animal species, immune status, pathogens selected, and route of administration, and study endpoints.

Balamuthia mandrillaris is an under-reported, pathogenic free-living amoeba that causes Balamuthia amoebic encephalitis (BAE) and cutaneous skin infections. Although cutaneous infections are not typically lethal, BAE with or without cutaneous involvement is usually fatal. This is due to the lack of drugs that are both efficacious and can cross the blood-brain barrier. We aimed to discover new leads for drug discovery by screening the open-source Medicines for Malaria Venture (MMV) Malaria Box and MMV Pathogen Box, with 800 compounds total. From an initial single point screen at 1 and 10 μM, we identified 54 hits that significantly inhibited the growth of B. mandrillaris in vitro. Hits were reconfirmed in quantitative dose-response assays and 23 compounds (42.6%) were confirmed with activity greater than miltefosine, the current standard of care.