Background: Cefepime is used for the treatment of nosocomial infections and serves as a carbapenem-sparing agent for treating AmpC inducible bacteria. Cefepime induced neurotoxicity (CIN) is a well-documented adverse effect, although data describing the risk of CIN in patients with a history of seizures (HOS) remains limited. Objectives: The primary and secondary objectives were to compare the rates of CIN in patients with and without HOS and identify risk factors associated with CIN, respectively. Methods: This was a retrospective matched cohort study of patients admitted to University Hospital from January 2019 to December 2022 that were initiated on cefepime with and without a baseline HOS. Patients were matched at a rate of 1:1 by age (+/- 5 years), sex, and month of admission (+/- 1 month). Results: A total of 150 patients were included, 75 in each group. There was no statistically significant difference in CIN between the two groups (9 vs 7, P = 0.7923). The only risk factors associated with CIN were age >65 (OR, 5.8 [95% CI, 1.194-27.996]), acute kidney injury (AKI) during cefepime administration (OR, 13.8 [95% CI, 2.528-75.206]), and an intensive care unit (ICU) stay (OR, 8.6 [95% CI, 1.735-42.624]). Conclusion: There was no increased risk of CIN observed in patients with HOS. Patients age >65, AKI while receiving cefepime and those admitted to the ICU were 5.8, 13.8, and 8.6 times more likely to experience CIN. These results suggest that it may be safe to administer cefepime to patients with HOS in the appropriate clinical setting.

The effectiveness of β-lactam antibiotics is increasingly threatened by resistant bacteria that harbor hydrolytic β-lactamase enzymes. Depending on the class of β-lactamase present, β-lactam hydrolysis can occur through one of two general molecular mechanisms. Metallo-β-lactamases (MBLs) require active site Zn2+ ions, whereas serine-β-lactamases (SBLs) deploy a catalytic serine residue. The result in both cases is drug inactivation via the opening of the β-lactam warhead of the antibiotic. MBLs confer resistance to most β-lactams and are non-susceptible to SBL inhibitors, including recently approved diazabicyclooctanes, such as avibactam; consequently, these enzymes represent a growing threat to public health. Aspergillomarasmine A (AMA), a fungal natural product, can rescue the activity of the β-lactam antibiotic meropenem against MBL-expressing bacterial strains. However, the effectiveness of this β-lactam/β-lactamase inhibitor combination against bacteria producing multiple β-lactamases remains unknown. We systematically investigated the efficacy of AMA/meropenem combination therapy with and without avibactam against 10 Escherichia coli and 10 Klebsiella pneumoniae laboratory strains tandemly expressing single MBL and SBL enzymes. Cell-based assays demonstrated that laboratory strains producing NDM-1 and KPC-2 carbapenemases were resistant to the AMA/meropenem combination but became drug-susceptible upon adding avibactam. We also probed these combinations against 30 clinical isolates expressing multiple β-lactamases. E. coli, Enterobacter cloacae, and K. pneumoniae clinical isolates were more susceptible to AMA, avibactam, and meropenem than Pseudomonas aeruginosa and Acinetobacter baumannii isolates. Overall, the results demonstrate that a triple combination of AMA/avibactam/meropenem has potential for empirical treatment of infections caused by multiple β-lactamase-producing bacteria, especially Enterobacterales.

Biocatalysis is a valuable industrial approach in active pharmaceutical ingredient (API) manufacturing for asymmetric induction and synthesis of chiral APIs. Herein, we investigated synthesis of a panel of microtubule-destabilising antiproliferative β-lactam enantiomers employing a commercially available immobilised Candida antarctica lipase B enzyme together with methanol and MTBE. The β-lactam ring remained intact during chiral kinetic resolution reactions, plausibly due to a bulky N-1 phenyl substituent on the β-lactam ring substrate. The predominant reaction mediated by CAL-B was methanol catalysed conversion of the β-lactam 3-acetoxy substituent to a 3-hydroxyl group, with preferential methanolysis of the 3S, 4S enantiomer. The unreacted substrate underwent progressive enantioenrichment to the 3R, 4R enantiomer. Substitution patterns on the B ring C3 meta position of the β-lactam scaffold greatly affected the rate of reaction. Halo substituents (fluoro-, chloro- and bromo-) reduced the rate of conversion compared to unsubstituted analogues, which in turn increased enantiomeric excess (ee). Ee values up to 86 % for the 3S, 4S 3-hydroxyl enantiomer were achieved. A double resolution approach for unreacted substrate yielded high ee values (>99 %) for the 3R, 4R 3-acetoxy enantiomer. CAL-B mediated methanolysis is a more sustainable method for resolution of racemic antiproliferative β-lactams compared to a previous technique of chiral diastereomeric resolution. Yields of β-lactams obtained using CAL-B are far superior than previously described, which will facilitate progression toward pre-clinical and clinical development. Biocatalysis is a useful tool in the toolbox of the medicinal chemist.

The synergetic strategy has created tremendous advantages in drug-resistance bacterial infection treatment, whereas challenges related to novel compound discovery and identifying drug-binding targets still remain. The mechanisms of antimicrobial resistance involving β-lactamase catalysis and the degradation of β-lactam antibiotics are being revealed, with relevant therapies promising to improve the efficacy of existing major classes of antibiotics in the foreseeable future. In this study, it is demonstrated that nordalbergin, a coumarin isolated from the wood bark of Dalbergia sissoo, efficiently potentiated the activities of β-lactam antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) by suppressing β-lactamase performance and improving the bacterial biofilm susceptibility to antibiotics. Nordalbergin was found to destabilize the cell membrane and promote its permeabilization. Moreover, nordalbergin efficiently improved the therapeutic efficacy of amoxicillin against MRSA pneumonia in mice, as supported by the lower bacterial load, attenuated pathological damage, and decreased inflammation level. These results demonstrate that nordalbergin might be a promising synergist of amoxicillin against MRSA infections. This study provided a new approach for developing potentiators for β-lactam antibiotics against MRSA infections.

Aim: To assess the impact of experimental conditions on free serum concentrations as determined by ultrafiltration and HPLC-DAD analysis in a wide range of antibiotics. Materials & methods: Relative centrifugation force (RCF), temperature, pH and buffer were varied and the results compared with the standard protocol (phosphate buffer pH 7.4, 37°C, 1000 × g). Results: Generally, at 10,000 × g the unbound fraction (fu) decreased with increasing molecular weight, and was lower at 22°C. In unbuffered serum, the fu of flucloxacillin or valproic acid was increased, that of basic or amphoteric drugs considerably decreased. Comparable results were obtained using phosphate or HEPES buffer except for drugs which form metal chelate complexes. Conclusion: Maintaining a physiological pH is more important than strictly maintaining body temperature.
[Box: see text].

The high-level resistance to next-generation β-lactams frequently found in Staphylococcus aureus isolates lacking mec, which encodes the transpeptidase PBP2a traditionally associated with methicillin-resistant Staphylococcus aureus (MRSA), has remained incompletely understood for decades. A new study by Lai et al. found that the co-occurrence of mutations in pbp4 and gdpP, which respectively cause increased PBP4-mediated cell wall crosslinking and elevated cyclic-di-AMP levels, produces synergistic β-lactam resistance rivaling that of PBP2a-producing MRSA (L.-Y. Lai, N. Satishkumar, S. Cardozo, V. Hemmadi, et al., mBio 15:e02889-23. 2024, https://doi.org/10.1128/mbio.02889-23). The combined mutations are sufficient to explain the high-level β-lactam resistance of some mec-lacking strains, but the mechanism of synergy remains elusive and an avenue for further research. Importantly, the authors establish that co-occurrence of these mutations leads to antibiotic therapy failure in a Caenorhabditis elegans infection model. These results underscore the need to consider this unique and novel β-lactam resistance mechanism during the clinical diagnosis of MRSA, rather than relying on mec as a diagnostic.

UNASSIGNED: The cross-reactivity problem between cephalosporins and penicillins has mainly been evaluated in the context of patients allergic to penicillins. However, we have little data regarding the opposite aspect of the problem, i.e. the cross-reactivity in subjects primarily sensitized to cephalosporins. This prospective study aims to evaluate the cross-reactivity to penicillins and some other cephalosporins in patients with immediate allergic reactions to cephalosporins.
UNASSIGNED: The study included 21 children with immediate allergic reactions to at least one cephalosporin. Skin testing was performed with a panel of minor and major determinant mixtures of penicillins and three commonly used cephalosporins (cephazoline, cefuroxime and ceftriaxone).
UNASSIGNED: The children had used 5.14±4.91 (1-15) times any beta-lactam antibiotic in the previous year and the most common cephalosporins accused were ceftriaxone (42.92%), and cefuroxime, cefazolin, cefixime, cefprozil and cefotaxime (9.5% each). Skin tests were positive for any cephalosporin in 14 (66.7%) subjects and penicillin allergens in 15 (71.4%) subjects. Totally, 85.7% of children with a positive allergy history to cephalosporins were found to be sensitive to either penicillin or any one of three cephalosporins.
UNASSIGNED: There seems to be a high risk of adverse reactions to penicillins and other cephalosporins in children with a history of type I hypersensitivity reaction to cephalosporins. Therefore, skin testing with both cephalosporins and penicillins should be performed in patients with a history of cephalosporin allergy.

The VITEK®2 AES β-lactam phenotypes of 488 Enterobacterales from North and Latin America generated by the VITEK®2 were compared to the resistance genotypes provided by whole genome sequencing (WGS). The AES provided phenotypic reports for 447 (91.6 %) isolates, including isolates harbouring carbapenemases (195; 43.6 %), ESBLs (103; 23.0 %) and transferable AmpCs (tAmpC; 28; 6.3 %) genes, as well as wildtype isolates (WT; 121; 27.1 %). Overall, the AES report was accurate for 433/447 (96.9 %) isolates. The AES accurately reported carbapenemase, ESBL, and tAmpC phenotypes for 93.7 %, 93.7 %, and 98.4 % of isolates, respectively, and sensitivity/specificity rates were 96.4 %/91.7 %, 98.1 %/92.4 %, 82.1 %/99.5 %, and 100 %/98.8 %. 14 isolates carrying carbapenemase (7 total; 3 KPC, 2 MBL, 2 OXA-48-like), ESBL (2), and tAmpC-encoding genes (5) were not correctly identified by AES. The AES phenotypic report detected resistance mechanisms among Enterobacterales rapidly and could significantly aid future antimicrobial stewardship initiatives and patient care.

The emergence of oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) has imposed further challenges to the clinical management of MRSA infections. When exposed to β-lactam antibiotics, these strains can easily acquire reduced β-lactam susceptibility through chromosomal mutations, including those in RNA polymerase (RNAP) genes such as rpoBC, which may then lead to treatment failure. Despite the increasing prevalence of such strains and the apparent challenges they pose for diagnosis and treatment, there is limited information available on the actual mechanisms underlying such chromosomal mutation-related transitions to reduced β-lactam susceptibility, as it does not directly associate with the expression of mecA. This study investigated the cellular physiology and metabolism of six missense mutants with reduced oxacillin susceptibility, each carrying respective mutations on RpoBH929P, RpoBQ645H, RpoCG950R, RpoCG498D, RpiAA64E, and FruBA211E, using capillary electrophoresis-mass spectrometry-based metabolomics analysis. Our results showed that rpoBC mutations caused RNAP transcription dysfunction, leading to an intracellular accumulation of ribonucleotides. These mutations also led to the accumulation of UDP-Glc/Gal and UDP-GlcNAc, which are precursors of UTP-associated peptidoglycan and wall teichoic acid. Excessive amounts of building blocks then contributed to the cell wall thickening of mutant strains, as observed in transmission electron microscopy, and ultimately resulted in decreased susceptibility to β-lactam in OS-MRSA.
OBJECTIVE: The emergence of oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) strains has created new challenges for treating MRSA infections. These strains can become resistant to β-lactam antibiotics through chromosomal mutations, including those in the RNA polymerase (RNAP) genes such as rpoBC, leading to treatment failure. This study investigated the mechanisms underlying reduced β-lactam susceptibility in four rpoBC mutants of OS-MRSA. The results showed that rpoBC mutations caused RNAP transcription dysfunction, leading to an intracellular accumulation of ribonucleotides and precursors of peptidoglycan as well as wall teichoic acid. This, in turn, caused thickening of the cell wall and ultimately resulted in decreased susceptibility to β-lactam in OS-MRSA. These findings provide insights into the mechanisms of antibiotic resistance in OS-MRSA and highlight the importance of continued research in developing effective treatments to combat antibiotic resistance.

The use of antimicrobials in poultry leaves residues in the litter, favoring the emergence of antimicrobial-resistant pathogens and making it a source of contamination. An in vitro 4 × 4 factorial trial was performed to investigate the influence of four treatments, consisting of antimicrobial sub-concentrations, on the transference of IncB/O-plasmid through conjugation in four groups. Each group was composed of one plasmid donor bacterium (Escherichia coli H2332) and a recipient bacterium (Escherichia coli J62 or Salmonella enterica serovars, Enteritidis, Typhimurium, or Heidelberg). Our results showed a little decrease in the conjugation frequency in almost all treatments between the two bacterial species, which varied according to each strain. The MIC test revealed an increase of up to 4096-fold in resistance to beta-lactams in Salmonella serovars after plasmid acquisition. This finding suggests that some genetic apparatus may be involved in increased antimicrobial resistance in Salmonella serovars after the acquisition of primary resistance determinants.