Penicillins

BackgroundHaemophilus influenzae is an opportunistic bacterial pathogen that can cause severe respiratory tract and invasive infections. The emergence of β-lactamase-negative ampicillin-resistant (BLNAR) strains and unclear correlations between genotypic (i.e., gBLNAR) and phenotypic resistance are challenging empirical treatments and patient management. Thus, we sought to revisit molecular resistance mechanisms and to identify new resistance determinants of H. influenzae.MethodsWe performed a systematic meta-analysis of H. influenzae isolates (n = 291) to quantify the association of phenotypic ampicillin and cefotaxime resistance with previously defined resistance groups, i.e., specific substitution patterns of the penicillin binding protein PBP3, encoded by ftsI. Using phylogenomics and a genome-wide association study (GWAS), we investigated evolutionary trajectories and novel resistance determinants in a public global cohort (n = 555) and a new clinical cohort from three European centers (n = 298), respectively.ResultsOur meta-analysis confirmed that PBP3 group II- and group III-related isolates were significantly associated with phenotypic resistance to ampicillin (p ConclusionsGradient agar diffusion strips and broth microdilution assays do not consistently classify isolates from PBP3 groups as phenotypically resistant. Consequently, when the minimum inhibitory concentration is close to the clinical breakpoints, and genotypic data is available, PBP3 resistance groups should be prioritized over susceptible phenotypic results for ampicillin. The implications on treatment outcome and bacterial fitness of other extended PBP3 substitution patterns and novel candidate genes need to be determined.

Metabolic state-reprogramming approach was extended from Gram-negative bacteria to Gram-positive bacterium methicillin-resistant Staphylococcus aureus (MRSA) for identifying desired reprogramming metabolites to synergize existing antibiotic killing to MRSA. Metabolomics comparison between MRSA and methicillin-sensitive Staphylococcus aureus showed a depressed metabolic state in MRSA. Valine was identified as the most depressed metabolite/biomarker, and valine, leucine and isoleucine biosynthesis as the most enriched metabolic pathway. Thus, valine was used as a reprogramming metabolite to potentiate existing antibiotic killing to MRSA. Among the tested antibiotics, valine synergized cefoperazone-sulbactam (SCF) to produce the greatest killing effect. The combined effect of SCF and valine was demonstrated in clinical MRSA isolates and in mouse systemic and thigh infection models. Underlying mechanisms were attributed to valine-induced the activation of the pyruvate cycle/the TCA cycle and fatty acid biosynthesis. The activated pyruvate cycle/the TCA cycle elevated proton motive force by NADH and the activated fatty acid biosynthesis promoted membrane permeability by lauric acid. Both together increased cefoperazone uptake, which outpaces efflux action and thereby intracellular drug is elevated to effectively kill MRSA. These results provide the combination of valine and SCF to produce a new drug candidate effective against MRSA.ImportanceMethicillin-resistant Staphylococcus aureus (MRSA) is possibly the most infamous example of antibiotic resistance and new antibiotics are urgently needed to control it. The present study used metabolic state-reprogramming approach to identify an ideal biomarker as an antibiotic adjuvant for reversing the metabolic state of MRSA. The most repressed valine was identified as the adjuvant. Exogenous valine most effectively potentiated cefoperazone-sulbactam (SCF) to kill MRSA in vitro and in vivo. Viability of 18 clinical MRSA isolates was reduced by the top 276.64-fold in the presence of valine and SCF. In mouse models, lower bacterial load in liver, spleen, kidney, thigh, and higher survival were determined in the SCF + valine than valine or SCF alone. Valine promoted MRSA to increase SCF uptake that overcomes the efflux and enzymatic hydrolysis. It also extended the PAE of SCF. These occur because valine activates the pyruvate cycle to elevate proton motive force by NADH and increases membrane permeability by lauric acid. Therefore, the combination of valine and SCF is a new drug candidate effective against MRSA.

The recent US Food and Drug Administration approval of pivmecillinam-an oral prodrug of the amidinopenicillin antibiotic mecillinam-presents a valuable opportunity to address the need for new treatments for uncomplicated urinary tract infection (uUTI). We report findings of a systematic literature review of the safety profile of pivmecillinam/mecillinam based on more than 40 years' experience, mainly in Europe and Canada, to describe its tolerability profile and identify any important safety signals. In total, 110 eligible publications were identified describing use of pivmecillinam/mecillinam as monotherapy or in combination, for treatment of uUTI or other infectious conditions. These studies revealed a benign safety and tolerability profile, awareness of which will inform treatment decisions as pivmecillinam is made available in the United States. Together with the evidence for efficacy of, and minimal resistance to, pivmecillinam, the findings of this review support the position of pivmecillinam as a first-line treatment for uUTI.

BackgroundStaphylococcus aureus bacteremia is associated with high mortality. Whether cefazolin or an antistaphylococcal penicillin should be preferred for the treatment of methicillin-susceptible S. aureus bacteremia is unclear.MethodsIn an ongoing international Bayesian adaptive platform trial, we conducted an open-label, randomized comparison of cefazolin with an antistaphylococcal penicillin (flucloxacillin or cloxacillin) in adult patients with penicillin-resistant, methicillin-susceptible S. aureus bacteremia. The primary outcome, which was evaluated with a hierarchical Bayesian logistic-regression model, was death from any cause within 90 days after enrollment in the platform. We assessed the posterior probability of the noninferiority of cefazolin to flucloxacillin or cloxacillin (with the criterion for noninferiority prespecified as an adjusted odds ratio of ResultsThis domain of the ongoing trial was conducted between February 17, 2022, and August 7, 2024, by which time the criterion for noninferiority had been met. Mortality at 90 days among adults who could be evaluated was 15.0% (97 deaths among 645 patients) in the cefazolin group and 17.0% (109 deaths among 642 patients) in the antistaphylococcal-penicillin group (adjusted odds ratio, 0.81; 95% credible interval, 0.59 to 1.12; probability of noninferiority, 99.2%; probability of superiority, 89.8%). Acute kidney injury occurred in 92 of 660 patients (13.9%) in the cefazolin group, as compared with 127 of 648 (19.6%) in the antistaphylococcal-penicillin group (adjusted odds ratio, 0.67; 95% credible interval, 0.50 to 0.89; probability of superiority, 99.7%).ConclusionsIn patients with methicillin-susceptible S. aureus bacteremia, cefazolin was noninferior to flucloxacillin or cloxacillin with respect to 90-day mortality and was associated with a lower incidence of acute kidney injury. (Funded by the National Health and Medical Research Council and others; SNAP ClinicalTrials.gov number, NCT05137119.).