Pertussis is a poorly controlled vaccine-preventable disease. Verifying outbreaks is challenging owing to nonspecific clinical presentations and imperfect diagnostic tests. Exclusive reliance on highly sensitive polymerase chain reaction has been associated with pseudo-outbreaks.

Contamination of specimens with vaccine derived Bordetella pertussis DNA from pediatric clinic surfaces likely resulted in misdiagnoses. Standard practices, liquid transport medium, and lack of polymerase chain reaction cutoffs for discerning weakly positive (contaminant) DNA are contributory, but modifiable factors. (Read the full article)

Vitamin D levels in the general population have decreased considerably over the past decade. The implications of maternal vitamin D insufficiency during pregnancy for offspring neurocognitive development remain unclear.

Studying a large sample and using a prospective longitudinal design, this study demonstrates a link between maternal vitamin D insufficiency during pregnancy and offspring language impairment. There was no association with childhood behavioral or emotional problems. (Read the full article)

Postpartum vitamin A supplementation is a strategy to combat vitamin A deficiency and seems to reduce maternal/infant morbidity and mortality. However, controversies exist regarding which dose has a greater efficacy, 200 000 IU (WHO protocol) or 400 000 IU (IVACG protocol).

In this study, postpartum maternal supplementation with 400 000 IU of vitamin A did not provide any additional beneficial effect in reducing infant morbidity compared with the standard dose of 200 000 IU. (Read the full article)

Prenatal methamphetamine exposure has been related to deficits in fetal growth, changes in infant neurobehavior, and fine motor deficits, but little is known about its developmental effects on behavior problems in early childhood.

This is the first prospective study to identify behavior problems associated with prenatal methamphetamine exposure. Mood difficulties and acting-out behavior are increased in exposed children by age 3 years. Early identification and intervention may prevent escalation into delinquency and psychopathology. (Read the full article)

There is no literature on the concentrations of vitamin B₆ vitamers in cerebrospinal fluid of preterm and term newborn infants. This knowledge, however, is highly important, because vitamin B₆ plays a pivotal role in brain development and functioning.

In cerebrospinal fluid of newborn infants, B₆ vitamer concentrations are strongly dependent on postmenstrual age, indicating that vitamin B₆ homeostasis in brain differs between preterm and term newborns. This has implications for the evaluation of epilepsy and vitamin B₆ deficiency. (Read the full article)

Vitamin D is essential for bone health and for cardiovascular and immune function. In critically ill adults, vitamin D deficiency is common and associated with sepsis and with higher critical illness severity. The influence on pediatric critical illness is unclear.

We found a high prevalence of vitamin D deficiency in critically ill children, which was associated with higher critical illness severity. Vitamin D deficiency was less common in younger patients, in non-Hispanic white patients, in patients admitted over the summer, and in children taking supplemental vitamin D, with increasing amounts being more protective. (Read the full article)

Vitamin D is a pleiotropic hormone important for proper functioning of multiple organs. Adult critical care studies have suggested vitamin D as a modifiable risk factor. No studies have investigated the prevalence, risk factors, or role in pediatric critical illness.

This study provides evidence that the majority of critically ill children have vitamin D deficiency at the time of PICU admission, and that lower levels are associated with hypocalcemia, catecholamine administration, significant fluid bolus requirements, and longer PICU admissions. (Read the full article)

Cholestasis predisposes to the development of fat-soluble vitamin (FSV) deficiency. D-α tocopheryl polyethylene glycol-1000 succinate and coadministered FSVs are absorbed in spite of cholestasis.

Infants with biliary atresia with total bilirubin >2 mg/dL are at risk for fat-soluble vitamin (FSV) deficiency. A multivitamin preparation containing d-α tocopheryl polyethylene glycol-1000 succinate alone is not effective in treating biochemical FSV insufficiency in cholestatic infants. (Read the full article)

A growing number of epidemiologic studies suggest that individuals with lower vitamin D levels are at higher risk of acute respiratory tract infection. Randomized controlled trials are needed to determine if vitamin D supplementation would decrease this risk.

In a randomized controlled trial of 247 Mongolian children with vitamin D deficiency in winter, with double-blinding and 99% follow-up, vitamin D supplementation significantly reduced the risk of acute respiratory tract infections. (Read the full article)

Forearm fractures are unique injuries which are associated with lower bone mineral density in adults and white children. The relationships among bone mineral density, 25-hydroxyvitamin D status, and risk for forearm fracture have not been investigated in African American children.

Our data support an association between both lower bone mineral density and vitamin D deficiency and increased odds of forearm fracture in African American children. Promotion of bone health is indicated in this population. (Read the full article)

Despite numerous preventive strategies including prophylaxis with 400 IU/day of vitamin D in recent years, the deficiency of vitamin D in infants is still a global health problem.

This study reveals that the risk of vitamin D deficiency is high in exclusively breastfed infants, especially in winter, despite vitamin D supplementation. Therefore, it is suggested that an adjustment of vitamin D dosage for seasonal variation might be necessary. (Read the full article)

Brain maturation processes of very premature children are adversely affected by serious neonatal infections. Differences in brain development persist into childhood and adolescence, and underpin widespread neurocognitive and behavioral deficits in very preterm children.

We present evidence for long-term beneficial effects of early nutritional intervention with glutamine in very preterm infants on brain development at 8 years of age, mediated by a decrease in the number of serious neonatal infections. (Read the full article)

The rising burden of allergy is most evident in infancy, indicating the importance of early exposures. Reduced vitamin D status in pregnancy has been associated with atopy and respiratory outcomes, but there is less information on other early allergic outcomes.

Cord blood 25-hydroxyvitamin D₃ concentrations <50 nmol/L were highly prevalent in an Australian population. Lower vitamin D levels were associated with increased risk of eczema at 12 months of age, whereas there was no association with sensitization or food allergy. (Read the full article)

Cow’s milk consumption has opposite effects on vitamin D and iron levels in children; however, the amount of cow’s milk intake required for sufficient stores of vitamin D and iron is poorly understood, and existing guidelines on consumption are unclear.

Two cups of cow’s milk per day is sufficient to maintain healthy vitamin D and iron stores for most children. Wintertime vitamin D supplementation appears particularly important among children with darker skin pigmentation. (Read the full article)

Adequate vitamin D is essential for skeletal health in developing children. Although excess body weight is associated with risk of vitamin D deficiency, the national prevalence of vitamin D deficiency in overweight and obese children is unknown.

Vitamin D deficiency is highly prevalent in overweight and obese children, and severely obese and minority children are disproportionately affected. There are many modifiable factors associated with vitamin D deficiency in overweight and obese children. (Read the full article)

The Supplemental Nutrition Assistance Program (SNAP) is the largest federal nutrition assistance program. Studies among adults suggest that SNAP participation may be associated with suboptimal diets. Few studies have extensively examined these associations among children.

SNAP participation was not associated with childhood obesity. SNAP children consumed diets poorer in some aspects than nonparticipants, but intake of some micronutrients was higher. The diets of both groups of low-income children were far from meeting dietary guidelines. (Read the full article)

Children with acute liver failure due to a single-dose acetaminophen exposure have a characteristic liver biochemistry profile of low conjugated bilirubin and high alanine aminotransferase, which is associated with a favorable clinical outcome when treated with N-acetylcysteine.

Children with acute liver failure associated with chronic acetaminophen exposure also have a similar liver biochemistry profile, but for unknown reasons, they have a poorer clinical outcome than patients with single-dose acetaminophen exposure. (Read the full article)

Hypovitaminosis D is common among children. Although there is prolific biochemical literature linking vitamin D to enteric immunologic function, there is a paucity of prospective data exploring the role of supplementation in prevention of diarrheal illnesses.

In a high-risk population, quarterly supplementation with 100 000 IU of vitamin D₃ did not reduce the risk for first or recurrent diarrheal illnesses in a population of children aged 1 to 29 months in a low-income inner city setting. (Read the full article)

Sharing human milk between those with an abundant supply and those seeking milk for their child may be growing in popularity, facilitated by Web sites recently established to link providers and recipients.

This study documents the potential for human milk shared via the Internet to cause infectious disease by estimating the extent of microbial contamination among samples purchased via a leading Internet Web site. (Read the full article)

Preterm infants are born with low serum levels and low body stores of tocopherol. Serum levels ≥0.5 mg/dL are required for protection against lipid peroxidation. Previous studies have shown good intestinal absorption of vitamin E given intragastrically to preterm infants.

Serum α-tocopherol increases after a single 50-IU/kg dose of vitamin E as dl-α-tocopheryl acetate given intragastrically to very preterm infants soon after birth; however, 30% of infants still have serum α-tocopherol level <0.5 mg/dL 24 hours after dosing. (Read the full article)

A serum 25-hydroxyvitamin D (25(OH)D) concentration of 20 ng/mL meets the requirements of at least 97.5% of the population older than 1 year. A recommended dietary intake to achieve this serum 25(OH)D concentration has not been established during infancy.

Daily maternal (during pregnancy) and then infant vitamin supplementation with 1000/400 IU or 2000/800 IU increases the proportion of infants with 25(OH)D ≥20 ng/mL during infancy with the higher dose sustaining this increase for longer. (Read the full article)

Studies have shown dysfunction in the baroreflex mechanism and the autonomic nervous system, particularly in the sympathetic nervous system, in the pathophysiology of chronic fatigue syndrome, postural orthostatic tachycardia syndrome, and syncope.

Vitamin B₁₂ deficiency is associated with postural orthostatic tachycardia syndrome in adolescence. (Read the full article)

Despite widespread prevalence of vitamin D deficiency, there is a paucity of evidence on the appropriate supplemental dose in preterm infants. Various professional organizations empirically recommend different doses of vitamin D, ranging from 400 to 1000 IU per day.

Daily vitamin D supplementation at a dose of 800 IU compared with 400 IU significantly reduces the prevalence of vitamin D deficiency in preterm infants. The clinical significance of achieving vitamin D sufficiency needs to be studied in larger trials. (Read the full article)

Many young children are at risk for caries, which is the most common chronic disease of childhood. As primary teeth begin to develop in utero, prenatal influences are believed to affect the integrity of enamel and subsequent resistance to decay.

This study shows, for the first time, that maternal prenatal 25-hydroxyvitamin D levels may have an influence on the primary dentition and the development of early childhood caries. Specifically, lower levels are associated with increased risk of caries in infants. (Read the full article)

The World Health Organization recommends using vaccination contacts to deliver high-dose vitamin A supplementation (VAS) to children aged 6 to 59 months. The effect of this policy on overall child mortality has not been assessed.

In this first randomized controlled trial of VAS at routine vaccination contacts after 6 months, VAS had no overall effect on mortality but was associated with reduced mortality in girls and increased mortality in boys. (Read the full article)

Vitamin K prophylaxis at birth is an effective intervention for preventing vitamin K deficiency bleeding.

Refusal of vitamin K is not common, but those who refuse are more likely to have a birth attended by a midwife, and deliver at home or in a birth center. They are also less likely to immunize their child. (Read the full article)

Micronutrient deficiencies, including deficiencies of vitamin B-12 and folate, are common worldwide and may be a contributing factor to the estimated 165 million stunted children.

Routine supplementation of vitamin B-12 improved linear and ponderal growth in subgroups of young Indian children. We provide evidence that vitamin B-12 deficiency is a contributor to poor growth in low- and middle-income countries. (Read the full article)

Sharing human milk between those with an abundant supply and those seeking milk for their child is growing in popularity, including that facilitated by Web sites established to link buyers and sellers.

This study documents that human milk purchased via the Internet can be contaminated with cow’s milk, which poses a potential risk to infants with allergy or intolerance to cow’s milk. (Read the full article)

The vitamin D concentration in breast milk of women taking 400 IU vitamin D per day is relatively low, leading to vitamin D deficiency in breastfeeding infants. As a result, the American Academy of Pediatrics recommends breastfeeding infant vitamin D supplementation within days after birth.

Maternal vitamin D supplementation alone with 6400 IU/day safely supplies breast milk with adequate vitamin D to satisfy the requirement of her nursing infant and offers an alternate strategy to direct infant supplementation. (Read the full article)

Objectives. The aim of this study was to assess the safety of early oral switch (EOS) prior to 14 days for low-risk Staphylococcus aureus bacteremia (LR-SAB), which is the primary treatment strategy employed at our institution. Usually recommended therapy is 14 days of intravenous (IV) antibiotics.

Methods. All patients with SAB at our hospital were identified between 1 January 2014 and 31 December 2018. Those meeting low-risk criteria (healthcare-associated, no evidence of deep infection or demonstrated involvement of prosthetic material, and no further positive blood cultures after 72-hours) were included in the study. The primary outcome was occurrence of a SAB-related complication within 90 days.

Results. There were 469 SAB episodes during the study period, 100 (21%) of whom met inclusion criteria. EOS was performed in 84 patients. In this group, line infection was the source in 79%, methicillin-susceptible S. aureus caused 95% of SABs and 74% of patients received IV flucloxacillin. The median duration of IV and oral antibiotics in the EOS group was 5 (IQR 4-6) and 10 days (IQR 9-14), respectively. Seventy-one percent of patients received flucloxacillin as their EOS agent. Overall, 86% of oral step-down therapy was with beta-lactams. One patient (1%) undergoing EOS had SAB relapse within 90 days. No deaths attributable to SAB occurred within 90 days.

Conclusions. In this low MRSA prevalence LR-SAB cohort, EOS was associated with a low incidence of SAB-related complications. This was achieved with oral beta-lactam therapy in most patients. Larger prospective studies are needed to confirm these findings.

QPX7728 is a new ultra-broad-spectrum inhibitor of serine and metallo beta-lactamases from a class of cyclic boronates that gave rise to vaborbactam. The spectrum and mechanism of beta-lactamase inhibition by QPX7728 were assessed using purified enzymes from all molecular classes. QPX7728 inhibits class A ESBLs (IC₅₀ range 1-3 nM) and carbapenemases such as KPC (IC₅₀ 2.9±0.4 nM) as well as class C P99 (IC₅₀ of 22±8 nM) with a potency that is comparable or higher than recently FDA approved BLIs avibactam, relebactam and vaborbactam. Unlike those other BLIs, QPX7728 is also a potent inhibitor of class D carbapenemases such as OXA-48 from Enterobacteriaceae and OXA enzymes from A. baumannii (OXA-23/24/58, IC₅₀ range 1-2 nM) as well as MBLs such as NDM-1 (IC₅₀ 55±25 nM), VIM-1 (IC₅₀ 14±4 nM) and IMP-1 (IC₅₀ 610±70 nM). Inhibition of serine enzymes by QPX7728 is associated with progressive inactivation with a high efficiency k₂/K ranging from of 6.3 x 10⁴ (for P99) to 9.9 x 10⁵ M^-1 s^-1 (for OXA-23). This inhibition is reversible with variable stability of the QPX7728-beta-lactamase complexes with target residence time ranging from minutes to several hours: 5-20 minutes for OXA carbapenemases from A. baumanii, ~50 minutes for OXA-48 and 2-3 hours for KPC and CTX-M-15. QPX7728 inhibited all tested serine enzymes at 1:1 molar ratio. Metallo-beta-lactamases NDM, VIM, and IMP were inhibited by a competitive mechanism with fast-on-fast-off kinetics, with K_is of 7.5±2.1 nM, 32±14 nM and 240±30 nM for VIM-1, NDM-1 and IMP-1, respectively. QPX7728 ultra-broad-spectrum of BLI inhibition combined with its high potency enables combinations with multiple different beta-lactam antibiotics.

β-lactam resistance in Staphylococcus aureus limits treatment options. Stp1 and Stk1, a serine-threonine phosphatase and kinase respectively, mediate serine-threonine kinase (STK) signaling. Loss of function point mutations in stp1 were detected among laboratory passaged, β-lactam resistant S. aureus strains lacking mecA and blaZ, the major determinants of β-lactam resistance in the bacteria. Loss of Stp1 function facilitates β-lactam resistance of the bacteria.

Carbapenem-resistant Gram-negative pathogens are a critical public health threat and there is an urgent need for new treatments. Carbapenemases (β-lactamases able to inactivate carbapenems) have been identified in both serine β-lactamase (SBL) and metallo β-lactamase (MBL) families. The recent introduction of SBL carbapenemase-inhibitors has provided alternative therapeutic options. Unfortunately, there are no approved inhibitors of MBL-mediated carbapenem-resistance and treatment options for infections caused by MBL-producing Gram-negatives are limited. Here, we present ZN148, a zinc-chelating MBL-inhibitor capable of restoring the bactericidal effect of meropenem and in vitro clinical susceptibility to carbapenems in >98% of a large international collection of MBL-producing clinical Enterobacterales strains (n=234). Moreover, ZN148 was able to potentiate the effect of meropenem against NDM-1-producing Klebsiella pneumoniae in a murine neutropenic peritonitis model. ZN148 showed no inhibition of the human zinc-containing enzyme glyoxylase II at 500 μM and no acute toxicity was observed in an in vivo mouse model with cumulative dosages up to 128 mg/kg. Biochemical analysis showed a time-dependent inhibition of MBLs by ZN148 and removal of zinc ions from the active site. Addition of exogenous zinc after ZN148 exposure only restored MBL activity by ~30%, suggesting an irreversible mechanism of inhibition. Mass-spectrometry and molecular modelling indicated potential oxidation of the active site Cys221 residue. Overall, these results demonstrate the therapeutic potential of a ZN148-carbapenem combination against MBL-producing Gram-negative pathogens and that ZN148 is a highly promising MBL inhibitor, capable of operating in a functional space not presently filled by any clinically approved compound.

Multi-drug resistance among Gram-negative bacteria is a major global public health threat. Metallo-β-lactamases (MBLs) target the most widely-used antibiotic class, the β-lactams, including the most recent-generation carbapenems. Interspecies spread renders these enzymes a serious clinical threat and there are no clinically-available inhibitors. We present crystal structures of IMP-13, a structurally-uncharacterized MBL from Gram-negative Pseudomonas aerugionasa found in clinical outbreaks globally, and characterize the binding using solution NMR-spectroscopy and molecular-dynamics simulations. Crystal structures of apo IMP-13 and bound to four clinically-relevant carbapenem antibiotics (doripenem, ertapenem, imipenem and meropenem) are presented. Active site plasticity and the active-site loop, where a tryptophan residue stabilizes the antibiotic core scaffold, are essential to the substrate-binding mechanism. The conserved carbapenem scaffold plays the most significant role in IMP-13 binding, explaining the broad substrate specificity. The observed plasticity and substrate-locking mechanism provide opportunities for rational drug design of novel metallo-β-lactamase inhibitors, essential in the fight against antibiotic resistance.

QPX7728 is an ultra-broad-spectrum boronic acid beta-lactamase inhibitor with potent inhibition of key serine and metallo beta-lactamases observed in biochemical assays. Microbiological studies using characterized strains were used to provide a comprehensive characterization of the spectrum of beta-lactamase inhibition by QPX7728. The MIC of multiple IV only (ceftazidime, piperacillin, cefepime, ceftolozane and meropenem) and orally bioavailable (ceftibuten, cefpodoxime, tebipenem) antibiotics alone and in combination with QPX7728 (4 μg/ml), as well as comparator agents, were determined against the panels of laboratory strains of P. aeruginosa and K. pneumoniae expressing over 55 diverse serine and metallo beta-lactamases. QPX7728 significantly enhanced the potency of antibiotics against the strains expressing Class A extended spectrum beta-lactamases (CTX-M, SHV, TEM, VEB, PER) and carbapenemases (KPC, SME, NMC-A, BKC-1), consistent with beta-lactamase inhibition demonstrated in biochemical assays. It also inhibits both plasmidic (CMY, FOX, MIR, DHA) and chromosomally encoded (P99, PDC, ADC) Class C beta-lactamases and Class D enzymes including carbapenemases such as OXA-48 from Enterobacteriaceae and OXA enzymes from Acinetobacter baumannii (OXA-23/24/72/58). QPX7728 is also a potent inhibitor of many class B metallo beta-lactamases (NDM, VIM, CcrA1, IMP, GIM but not SPM or L1). Addition of QPX7728 (4 μg/ml) reduced the MICs in a majority of strains to the level observed for the vector alone control, indicative of complete beta-lactamase inhibition. The ultra-broad-spectrum beta-lactamase inhibition profile makes QPX7728 a viable candidate for further development.

The Cpx stress response is widespread among Enterobacteriaceae. We have previously reported a mutation in cpxA in a multidrug resistant strain of Klebsiella aerogenes isolated from a patient treated with imipenem. This mutation yields to a single amino acid substitution (Y144N) located in the periplasmic sensor domain of CpxA. In this work, we sought to characterize this mutation in Escherichia coli by using genetic and biochemical approaches. Here, we show that cpxA^Y144N is an activated allele that confers resistance to β-lactams and aminoglycosides in a CpxR-dependent manner, by regulating the expression of the OmpF porin and the AcrD efflux pump, respectively. We also demonstrate the intimate interconnection between Cpx system and peptidoglycan integrity on the expression of an exogenous AmpC β-lactamase by using imipenem as a cell wall active antibiotic or inactivation of penicillin-binding proteins. Moreover, our data indicate that the Y144N substitution abrogates the interaction between CpxA and CpxP and increase phosphotransfer activity on CpxR. Because the addition of a strong AmpC inducer such as imipenem is known to causes abnormal accumulation of muropeptides (disaccharide-pentapeptide, N-acetylglucosamyl-1,6-anhydro-N-acetylmuramyl-l-alanyl-d-glutamy-meso-diaminopimelic-acid-d-alanyl-d-alanine) in the periplasmic space, we propose these molecules activate the Cpx system by displacing CpxP from the sensor domain of CpxA. Altogether, these data could explain why large perturbations to peptidoglycan caused by imipenem lead to mutational activation of the Cpx system and bacterial adaptation through multidrug resistance. These results also validate the Cpx system, in particular the interaction between CpxA and CpxP, as a promising therapeutic target.

QPX7728 is an ultra-broad-spectrum boronic acid beta-lactamase inhibitor that demonstrates inhibition of key serine and metallo beta-lactamases at a nano molar range in biochemical assays with purified enzymes. The broad-spectrum inhibitory activity of QPX7728 observed in biochemical experiments translates into enhancement of the potency of many beta-lactams against strains of target pathogens producing beta-lactamases. The impact of bacterial efflux and permeability on inhibitory potency were determined using isogenic panels of KPC-3 producing isogenic strains of K. pneumoniae and P. aeruginosa and OXA-23-producing strains of A. baumannii with various combinations of efflux and porin mutations. QPX7728 was minimally affected by multi-drug resistance efflux pumps in either Enterobacteriaceae, or in non-fermenters such as P. aeruginosa or A. baumannii. In P. aeruginosa, the potency of QPX7728 was further enhanced when the outer membrane is permeabilized. The potency of QPX7728 in P. aeruginosa is not affected by inactivation of the carbapenem porin OprD. While changes in OmpK36 (but not OmpK35) reduced the potency of QPX7728 (8-16-fold), QPX7728 (4 μg/ml) nevertheless completely reversed KPC-mediated meropenem resistance in strains with porin mutations, consistent with a lesser effect of these mutations on the potency of QPX7728 compared to other agents. The ultra-broad-spectrum beta-lactamase inhibition profile combined with enhancement of the activity of multiple beta-lactam antibiotics with varying sensitivity to the intrinsic resistance mechanisms of efflux and permeability indicate QPX7728 is a useful inhibitor for use with multiple beta-lactam antibiotics.

Third-generation cephalosporin (3GC)-resistant Enterobacteriaceae are classified as critical priority pathogens, with extended-spectrum β-lactamases (ESBLs) as principal resistance determinants. Enmetazobactam (formerly AAI101) is a novel ESBL inhibitor developed in combination with cefepime for empiric treatment of serious Gram-negative infections in settings where ESBLs are prevalent. Cefepime-enmetazobactam has been investigated in a phase 3 trial in patients with complicated urinary tract infections or acute pyelonephritis. This study examined pharmacokinetic-pharmacodynamic (PK-PD) relationships of enmetazobactam, in combination with cefepime, for ESBL-producing isolates of Klebsiella pneumoniae in 26-hour murine neutropenic thigh infection models. Enmetazobactam dose fractionation identified time above a free threshold concentration (fT > C_T) as the PK-PD index predictive of efficacy. Nine ESBL-producing isolates of K. pneumoniae, resistant to cefepime and piperacillin-tazobactam, were included in enmetazobactam dose-ranging studies. The isolates encoded CTX-M-type, SHV-12, DHA-1 and OXA-48 β-lactamases and covered a cefepime-enmetazobactam MIC range from 0.06 to 2 μg/ml. Enmetazobactam restored the efficacy of cefepime against all isolates tested. Sigmoid curve fitting across the combined set of isolates identified enmetazobactam PK-PD targets for stasis and for a 1-log₁₀ bioburden reduction of 8% and 44% fT > 2 μg/ml, respectively, with a concomitant cefepime PK-PD target of 40 – 60% fT > cefepime-enmetazobactam MIC. These findings support clinical dose selection and breakpoint setting for cefepime-enmetazobactam.

Klebsiella pneumoniae that produce extended spectrum beta lactamases (ESBLs) are a persistent public health threat. There are relatively few therapeutic options and there is undue reliance on carbapenems. Alternative therapeutic options are urgently required. A combination of cefepime and the novel beta lactamase inhibitor enmetazobactam is being developed for treatment of serious infections caused by ESBL-producing organisms. The pharmacokinetics-pharmacodynamics (PK-PD) of cefepime-enmetazobactam against ESBL-producing K. pneumoniae was studied in a neutropenic murine pneumonia model. Dose ranging studies were performed. Dose fractionation studies were performed to define the relevant PD index for the inhibitor. The partitioning of cefepime and enmetazobactam into the lung was determined by comparing area under the concentration time curve (AUC) in plasma and epithelial lining fluid. The magnitude of drug exposure for cefepime-enmetazobactam required for logarithmic killing in the lung was defined using 3 ESBL-producing strains. Cefepime 100 mg/kg q8h i.v. had minimal antimicrobial effect. When this background regimen of cefepime was combined with enmetazobactam half-maximal effect was induced with enmetazobactam 4.71 mg/kg q8h i.v. The dose fractionation study suggest both fT>threshold and fAUC:MIC are potentially relevant PD indices. The AUC_ELF:AUC_plasma for cefepime and enmetazobactam was 73.4% and 61.5%, respectively. A ≥2-log kill in the lung was achieved with a plasma and ELF cefepime fT>MIC of ≥20% and enmetazobactam fT>2 mg/L of ≥20% of the dosing interval. These data and analyses provide the underpinning evidence for the combined use of cefepime and enmetazobactam for nosocomial pneumonia.

Chromosomal and plasmid-borne AmpC cephalosporinases are a major resistance mechanism to β-lactams in Enterobacteriaceae and Pseudomonas aeruginosa. The new β-lactamase inhibitor avibactam effectively inhibits class C enzymes and can fully restore ceftazidime susceptibility. The conserved amino acid residue Asn³⁴⁶ of AmpC cephalosporinases directly interacts with the avibactam sulfonate. Disruption of this interaction caused by the N³⁴⁶Y amino acid substitution in Citrobacter freundii AmpC was previously shown to confer resistance to the ceftazidime-avibactam combination (CAZ-AVI). The aim of this study was to phenotypically and biochemically characterize the consequences of the N³⁴⁶Y substitution in various AmpC backgrounds. Introduction of N³⁴⁶Y into Enterobacter cloacae AmpC (AmpC_cloacae), plasmid-mediated DHA-1, and P. aeruginosa PDC-5, led to 270-, 12,000-, and 79-fold decreases in the inhibitory efficacy (k₂/K_i) of avibactam, respectively. The kinetic parameters of AmpC_cloacaeand DHA-1 for ceftazidime hydrolysis were moderately affected by the substitution. Accordingly, AmpC_cloacaeand DHA-1 harboring N³⁴⁶Y conferred CAZ-AVI resistance (MIC of ceftazidime of 16 µg/ml in the presence of 4 µg/ml of avibactam). In contrast, production of PDC-5 N³⁴⁶Y was associated with a lower MIC (4 µg/ml) since this β-lactamase retained a higher inactivation efficacy by avibactam in comparison to AmpC_cloacaeN³⁴⁶Y. For FOX-3, the I³⁴⁶Y substitution did not reduce the inactivation efficacy of avibactam and the substitution was highly deleterious for β-lactam hydrolysis, including ceftazidime, preventing CAZ-AVI resistance. Since AmpC_cloacaeand DHA-1 display substantial sequence diversity, our results suggest that loss of hydrogen interaction between Asn³⁴⁶ and avibactam could be a common mechanism of acquisition of CAZ-AVI resistance.

Durlobactam (DUR, also known as ETX2514) is a novel β-lactamase inhibitor with broad activity against Ambler class A, C, and D β-lactamases. Addition of DUR to sulbactam (SUL) in vitro restores SUL activity against clinical isolates of Acinetobacter baumannii. The safety and pharmacokinetics (PK) of DUR alone and with SUL and/or imipenem/cilastatin (IMI/CIL) were evaluated in healthy subjects. This was a randomized, placebo-controlled study. In Part A, subjects including an elderly cohort (DUR 1 g) received single ascending doses of DUR 0.25-8 g. In Part B, multiple ascending dose of DUR 0.25-2 g were administered every 6 hours (q6h) for 29 doses. In Parts C and D, the drug-drug interaction (DDI) potential, including safety, of DUR (1 g) with SUL (1 g) and/or IMI/CIL (0.5/0.5 g) was investigated after single and multiple doses. Plasma and urine concentrations of DUR, SUL, and IMI/CIL were determined. Among 124 subjects, DUR was generally safe and well tolerated either alone or in combination with SUL and/or IMI/CIL. After single and multiple doses, DUR demonstrated linear dose proportional exposure across the studied dose ranges. Renal excretion was a predominant clearance mechanism. No drug:drug interaction potential was identified between DUR and SUL and/or IMI/CIL. SUL-DUR, 1 g (of each component) administered q6h with a 3 hour IV infusion, is under development for the treatment of serious infections due to A. baumannii.

Ceftazidime–avibactam and cefiderocol are two of the latest generation β-lactam agents that possess expanded activity against highly drug-resistant bacteria, including carbapenem-resistant Enterobacterales. Here we show that structural changes in AmpC β-lactamases can confer reduced susceptibility to both agents. A multidrug-resistant Enterobacter cloacae clinical strain (Ent385) was found to be resistant to ceftazidime–avibactam and cefiderocol without prior exposure to either agent. The AmpC β-lactamase of Ent385 (AmpC^Ent385) contained an alanine–proline deletion at positions 294–295 (A294_P295del) in the R2 loop. AmpC^Ent385 conferred reduced susceptibility to ceftazidime–avibactam and cefiderocol when cloned into Escherichia coli TOP10. Purified AmpC^Ent385 showed increased hydrolysis of ceftazidime and cefiderocol compared with AmpC^Ent385Rev, in which the deletion was reverted. Comparisons of crystal structures of AmpC^Ent385 and AmpC^P99, the canonical AmpC of E. cloacae, revealed that the two-residue deletion in AmpC^Ent385 induced drastic structural changes of the H-9 and H-10 helices and the R2 loop, which accounted for the increased hydrolysis of ceftazidime and cefiderocol. The potential for a single mutation in ampC to confer reduced susceptibility to both ceftazidime–avibactam and cefiderocol requires close monitoring.

Importance Ceftazidime–avibactam and cefiderocol are newly approved β-lactam agents that possess broad spectrum activity against multidrug-resistant (MDR) Gram-negative bacteria. We show here that a two amino-acid deletion in the chromosomal AmpC β-lactamase, identified in a clinical strain of Enterobacter cloacae, confers reduced susceptibility to both agents. By crystallographic studies of free and drug-bound forms of enzyme, we demonstrate that this deletion in AmpC induces slanting of the H-9 helix that is directly connected with the R2 loop, and disappearance of the H-10 helix, is directly responsible for increased hydrolysis of ceftazidime and cefiderocol. These findings provide novel insights into how MDR Gram-negative bacteria may evolve their β-lactamases to survive selective pressure from these newly developed β-lactam agents.

The SHV β-lactamases (BLs) have undergone strong allele diversification that changed their substrate specificities. Based on 147 NCBI entries for SHV alleles, in silico mathematical models predicted five positions as relevant for the β-lactamase inhibitor (BLI) resistant (2br) phenotype, 12 as relevant for the extended-spectrum BL (ESBL) (2be) phenotype, and two positions were related to solely the narrow spectrum (2b) phenotype. These positions and additional 6 positions described in other studies (including one promoter mutation), were systematically substituted and investigated for their substrate specificities in a BL-free E. coli background, representing, to our knowledge, the most comprehensive substrate and substitution analysis for SHV alleles to date. An in vitro analysis confirmed the essentiality of the positions 238 and 179 for the 2be phenotype and 69 for the 2br phenotype. The substitutions E240K and E240R, which do not occur alone in known 2br SHV variants, led to a 2br phenotype, indicating a latent BLI-resistance potential of these substitutions. The substitutions M129V, A234G, S271I and R292Q conferred latent resistance to cefotaxime. In addition, 7 positions that were found to be not always associated with the ESBL phenotype resulted in increased resistance to ceftaroline. We also observed that coupling of a strong promoter (IS26) to a A146V mutant with the 2b phenotype resulted in a highly increased resistance to BLIs, cefepime and ceftaroline but not to 3^rd generation cephalosporins, indicating that SHV enzymes represent an underestimated risk for empirical therapies that use piperacillin/tazobactam or cefepime to treat different infectious diseases caused by gram-negatives.

A total of 2,283 Salmonella spp. isolates were recovered from 18,334 samples including patients with diarrhea, food of animal origin and pets across 5 provinces of China. The highest prevalence of Salmonella spp. was detected in chicken meats (39.3%, 486/1,237). Fifteen serogroups and 66 serovars were identified, with Typhimurium and Enteritidis being the most dominant. Most (85.5%, 1,952/2,283) isolates exhibited resistant to ≥ 1 antimicrobial and 56.4% were multi-drug resistant (MDR). A total of 222 isolates harbored extended-spectrum β-lactamases (ESBLs), 200 of which were CTX-M-type that were mostly detected from chicken meat and turtle fecal. Overall, eight bla_CTX-M genes were identified, with bla_CTX-M-65, bla_CTX-M-123, bla_CTX-M-14, bla_CTX-M-79, and bla_CTX-M-130 being the most prevalent. Totally, 166 of the 222 ESBL-producing isolates had amino acid substitutions in GyrA (S83Y, S83F, D87G, D87N, and D87Y) and ParC (and S80I), whilst the PMQR-encoding genes oqxA/B, qepA, and qnrB/S were detected in almost all isolates. Of the fifteen sequence types (STs) identified in the 222 ESBLs, ST17, ST11, ST34, and ST26 ranked among the top 5 in the number of isolates. Our study revealed considerable serovars diversity, high prevalence of co-occurrence of MDR determinants, including CTX-M-type ESBLs, QRDRs mutations and PMQR genes. This is the first report of CTX-M-130 Salmonella spp. from patients with diarrhea and QRDRs mutations from turtle fecal samples. Our study emphasizes the importance of actions, both in the health care settings and in the veterinary medicine sector, to control the dissemination of MDR, especially the CTX-M Salmonella spp. isolates.

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI) are associated with substantial morbidity and mortality. Monotherapy with first-line antimicrobials such as vancomycin (VAN; glycopeptide) and daptomycin (DAP; lipopeptide) are inadequate in some cases due to reduced antibiotic susceptibilities or therapeutic failure. In recent years, β-lactam antibiotics have emerged as a potential option for combination therapy with VAN/DAP that may meet an unmet therapeutic need for MRSA BSI. Ceftaroline (CPT), the only commercially available β-lactam in the United States with intrinsic in vitro activity against MRSA, has been increasingly studied in the setting of VAN and DAP failures. Novel combinations of first-line agents (VAN and DAP) with β-lactams have been the subject of many recent investigations due to in vitro findings such as the "see-saw effect", where β-lactam susceptibility may be improved in the presence of decreased glycopeptide and lipopeptide susceptibility. The combination of CPT and DAP, in particular, has become the focus of many scientific evaluations, due to intrinsic anti-MRSA activities and potent in vitro synergistic activity against various MRSA strains. This article reviews the available literature describing these innovative therapeutic approaches for MRSA BSI, focusing on preclinical and clinical studies, and evaluates the potential benefits and limitations of each strategy.

Meropenem/vaborbactam resistance in Klebsiella pneumoniae is associated with loss of function mutations in the OmpK35 and OmpK36 porins. Here we identify two previously unknown loss of function mutations that confer cefuroxime resistance in K. pneumoniae. The proteins lost were NlpD and KvrA; the latter is a transcriptional repressor controlling capsule production. We demonstrate that KvrA loss reduces OmpK35 and OmpK36 porin production, which confers reduced susceptibility to meropenem/vaborbactam in a KPC-3 producing K. pneumoniae isolate.

Methicillin-resistant Staphylococcus aureus (MRSA) has grown to become a major burden on healthcare systems. The cumulation of limited therapeutic options and worsened patient outcomes with persistent MRSA bacteremia has driven research in optimizing its initial management. The guidelines published by the Infectious Disease of America currently recommend combination therapy for refractory MRSA bacteremia, but the utility of combining antibiotics from the start of therapy is under investigation. The alternative strategy of early use of a β-lactam antibiotics in combination with vancomycin upon initial MRSA bacteremia detection has shown promise. While this concept has gained international attention, providers should give this strategy serious consideration prior to implementation. The objective of this review is to examine retrospective and prospective evidence for early combination with vancomycin and β-lactam antibiotics, as well as explore potential consequences of combination therapy.

A new protocol using aerosolized hydrogen peroxide to decontaminate N95 respirators could allow them to be safely reused in hospital settings. The protocol, optimized by a team of Penn State researchers, inactivates viruses without deforming or damaging the respirator and could help hospitals overcome the current respirator shortage due to the COVID-19 pandemic.

Millicent Collins
Aug 1, 2017; 140:e20160719-e20160719
CASE REPORTS

WHEN Tamsin Calidas stepped aboard a ferry bound for the Hebridean island that would become her new home, it was with hope for a fresh beginning, one far from the tumultuous events and near-death experience she had faced in the city streets being left behind.