Treatment of Mycobacterium abscessus pulmonary disease requires multiple antibiotics including intravenous β-lactams (e.g., imipenem). M. abscessus produces a β-lactamase (BlaMab) that inactivates β-lactam drugs but less efficiently carbapenems. Due to intrinsic and acquired resistance in M. abscessus and poor clinical outcomes, it is critical to understand the development of antibiotic resistance both within the host and in the setting of outbreaks. We compared serial longitudinally collected M. abscessus subsp. massiliense isolates from the index case of a cystic fibrosis center outbreak and four outbreak-related strains. We found strikingly high imipenem resistance in the later patient isolates, including the outbreak strain (MIC > 512 µg/mL). The phenomenon was recapitulated upon exposure of intracellular bacteria to imipenem. Addition of the β-lactamase inhibitor avibactam abrogated the resistant phenotype. Imipenem resistance was caused by an increase in β-lactamase activity and increased blaMab mRNA level. Concurrent increase in transcription of the preceding ppiA gene indicated upregulation of the entire operon in the resistant strains. Deletion of the porin mspA coincided with the first increase in MIC (from 8 to 32 µg/mL). A frameshift mutation in msp2 responsible for the rough colony morphology and a SNP in ATP-dependent helicase hrpA cooccurred with the second increase in MIC (from 32 to 256 µg/mL). Increased BlaMab expression and enzymatic activity may have been due to altered regulation of the ppiA-blaMab operon by the mutated HrpA alone or in combination with other genes described above. This work supports using carbapenem/β-lactamase inhibitor combinations for treating M. abscessus, particularly imipenem-resistant strains.

In Japan, only ampicillin/cloxacillin (ABPC/MCIPC) is available as an anti-staphylococcal penicillin-based treatment for Staphylococcus aureus bacteremia. However, the incidence of adverse events associated with double beta-lactam administration remains unknown. Therefore, we investigated the adverse events of double beta-lactam administration in patients with bacteremia. Adult patients (≥18 years) with bacteremia treated with ABPC, ABPC + ceftriaxone (CTRX), or ABPC/MCIPC were retrospectively analyzed. The primary outcome of this study was the incidence of adverse events such as acute kidney injury, liver dysfunction, and myelosuppression. Chi-square tests and t-tests were used for bivariate analysis. Propensity score (PS) matching was conducted to adjust for confounding factors. We included 277 ABPC-, 57 ABPC + CTRX-, and 43 ABPC/MCIPC-treated patients. Significant differences were noted in age, number of male patients, proportion of patients with qSOFA score ≥2, incidence of chronic kidney disease, treatment duration, mechanical ventilation use, vasopressor use, and proportion of patients with acute kidney injury (AKI) KDIGO grade ≥2. Further, a significant difference was observed between ABPC and ABPC/MCIPC, with a hazard ratio of 1.83 in AKI. In the PS-matched cohort, AKI incidence associated with ABPC/MCIPC was significantly higher than that associated with ABPC. ABPC + CTRX may be safe, whereas ABPC/MCIPC presents a higher risk of AKI and may not be suitable.

Introduction: Aminoglycosides possess activity against aerobic gram-negative organisms and are often used in combination with beta-lactam antibiotics. Previous studies evaluating combination therapy in gram-negative bacteremia have not shown clear benefits, however antimicrobial resistance was not prevalent in these studies. Our objective is to elucidate potential benefits of adding a single dose of an aminoglycoside to a beta-lactam in patients with gram-negative bacteremia. Methods: This study was a single-center, retrospective, cohort study including patients 18 years old or older and treated for at least 24 hours for a confirmed gram-negative bacteremia. Patients were divided into two groups: receipt of beta-lactam monotherapy (n = 164) and receipt of a beta-lactam in addition to a single dose of an aminoglycoside (n = 79) within 24 hours of bacteremia onset. The primary endpoint was infection-related 30-day mortality per provider documentation. Key secondary outcomes include incidence of acute kidney injury (AKI) and time to improvement of AKI. Data were analyzed using Chi-square or Fisher\'s exact tests, student\'s T test, and descriptive statistics as appropriate. Results: The primary outcome occurred in 13/164 vs 2/79 patients in the monotherapy and combination groups (P = 0.10). Incidence of AKI (14% vs. 12%) and time to recovery from AKI (90 hours; IQR [50 - 133] vs 78 hours; IQR [42 - 128]) were comparable between groups (P = 1.00 and P = 0.73, respectively). Conclusions: The addition of a single-dose aminoglycoside was not significantly associated with reduced mortality or increased time to recovery from AKI in our patient population. Larger studies, particularly in more severely ill patient populations, are needed.

BACKGROUND: There is a scarcity of prospective studies investigating the relative roles of skin prick and intradermal testing, serum-specific Immunoglobulin E, and extended oral challenges in diagnosing children with reported beta-lactam allergies.
OBJECTIVE: To determine the sensitivity and specificity of skin testing and serum-specific Immunoglobulin E in children with beta-lactam allergies, with immediate and non-immediate historic reactions.
METHODS: Four hundred children with parent-reported beta-lactam allergies were recruited into an open-label prospective study. Detailed allergy histories were collected. Those with medically observed and documented histories of anaphylaxis, requiring epinephrine, or SCARs were excluded. In total, 380 children underwent all testing modalities and a direct provocation test. Each child was followed up for a minimum of three years.
RESULTS: True allergy in children was uncommon, 8·3% reacted to the direct provocation challenge or the 5-day extended oral provocation challenge. Children reporting cephalosporin allergy or a reaction within one year were more likely to react to direct provocation testing. The sensitivity, specificity, and positive predictive value of skin testing was 12·5%, 98·8% and 20·0% for direct challenge outcomes, 4·76%, 99·0% and 25·0% for extended challenge outcomes, and 6·9%, 99·0% and 40·0% for both challenges combined. Follow-up investigations revealed that 5·7% of children had a mild repeat reaction and 2·7% continued to avoid the culprit despite successful delabeling. The relabeling rate for children readmitted to hospital was 15% with the relabeing being unfounded.
CONCLUSIONS: Genuine beta-lactam allergies were rare, with over 90% of children effectively delabeled. Skin and serum-specific Immunoglobulin E testing did not aid the diagnosis of beta-lactam antibiotic allergy in children, regardless of medical history. Extended oral challenges proved valuable in confirming allergies and boosted parental confidence.

OBJECTIVE: The purpose of this study was to define current practices related to beta-lactam/beta-lactamase inhibitor (BL/BLI) dose descriptions in hospitals that provide care for pediatric patients and to identify perceived implications of standardizing BL/BLI dose communication and ordering to a total drug-based strategy.
METHODS: A 27-item electronic survey was distributed via 4 pediatric pharmacy and infectious diseases listservs. Survey questions pertained to hospital demographics, dosing communication practices, BL/BLI ordering and labeling practices, obstacles to safe BL/BLI use, and the effects of potential standardization to a total drug communication strategy. SPSS was used for quantitative analysis and MAXQDA was used for qualitative analysis.
RESULTS: A total of 140 unique survey responses were analyzed after exclusion of incomplete responses and reconciliation of multiple responses from the same institution. Overall, 56.2% of institutions order BL/BLIs by BL component for pediatric patients, and 22% of institutions order by BL component for adult patients. Approximately half (51.8%) of respondents felt that standardizing to total drug would have a negative effect at their institution; perception of potential effect varied based on the institution\'s ordering strategy.
CONCLUSIONS: Communication and ordering of BL/BLIs is inconsistent across institutions and between pediatric and adult patients. In the short term, the perception is that standardization would compound institutional challenges.

UNASSIGNED: Given the negative consequences associated with a penicillin allergy label, broader penicillin allergy delabeling initiatives are highly desirable but hindered by the shortage of allergists in the United States. To address this problem at our facility, the infectious diseases section introduced a quality improvement initiative to evaluate and remove allergy labels among inpatient veterans.
UNASSIGNED: Between 15 November 2022 and 15 December 2023, we identified inpatients with a penicillin allergy label. We subsequently interviewed eligible candidates to stratify penicillin allergy risk and attempt to remove the allergy label directly via chart review, following inpatient oral amoxicillin challenge or outpatient community care allergy referral. Delabeling outcomes, subsequent penicillin-class prescriptions, and relabeling were tracked after successful allergy label removal.
UNASSIGNED: We screened 272 veterans, of whom 154 were interviewed for this intervention. A total of 53 patients were delabeled: 26 directly, 23 following oral amoxicillin challenge, and 4 following outpatient allergy referrals. Of the patients who were delabeled, 25 received subsequent penicillin-class prescriptions. No adverse reactions occurred following inpatient oral amoxicillin challenges. Patients with a low-risk penicillin allergy history were more likely to undergo a challenge if admitted with an infectious diseases-related condition. Only 1 inappropriate relabeling event occurred during the study period, which was subsequently corrected.
UNASSIGNED: An infectious diseases provider-led initiative resulted in penicillin allergy label removal in more than one third of inpatients evaluated using direct removal or oral amoxicillin challenge. Efforts focused on patients who had been admitted for infections were particularly successful.

UNASSIGNED: β-Lactams are the most widely used antibiotics in children. Their optimal dosing is essential to maximize their efficacy, while minimizing the risk for toxicity and the further emergence of antimicrobial resistance. However, most β-lactams were developed and licensed long before regulatory changes mandated pharmacokinetic studies in children. As a result, pediatric dosing practices are poorly harmonized and off-label use remains common today.
UNASSIGNED: β-Lactam pharmacokinetics and dose optimization strategies in pediatrics, including fixed dose regimens, therapeutic drug monitoring, and model-informed precision dosing are reviewed.
UNASSIGNED: Standard pediatric doses can result in subtherapeutic exposure and non-target attainment for specific patient subpopulations (neonates, critically ill children, e.g.). Such patients could benefit greatly from more individualized approaches to dose optimization, beyond a relatively simple dose adaptation based on weight, age, or renal function. In this context, Therapeutic Drug Monitoring (TDM) and Model-Informed Precision Dosing (MIPD) emerge as particularly promising avenues. Obstacles to their implementation include the lack of strong evidence of clinical benefit due to the paucity of randomized clinical trials, of standardized assays for monitoring concentrations, or of adequate markers for renal function. The development of precision medicine tools is urgently needed to individualize therapy in vulnerable pediatric subpopulations.

Current antibiograms cannot discern the particular effect of a specific antibiotic when the bacteria are incubated with a mixture of antibiotics. To prove that this task is achievable, Escherichia coli strains were treated with ciprofloxacin for 45 min, immobilized on a slide and stained with SYBR Gold. In susceptible strains, the nucleoid relative surface started to decrease near the MIC, being progressively condensed as the dose increased. The shrinkage level correlated with the DNA fragmentation degree. Ciprofloxacin-resistant bacilli showed no change. Additionally, E. coli strains were incubated with ampicillin for 45 min and processed similarly. The ampicillin-susceptible strain revealed intercellular DNA fragments that increased with dose, unlike the resistant strain. Co-incubation with both antibiotics revealed that ampicillin did not modify the nucleoid condensation effect of ciprofloxacin, whereas the quinolone partially decreased the background of DNA fragments induced by ampicillin. Sixty clinical isolates, with different combinations of susceptibility-resistance to each antibiotic, were co-incubated with the EUCAST breakpoints of susceptibility of ciprofloxacin and ampicillin. The morphological assay correctly categorized all the strains for each antibiotic in 60 min, demonstrating the feasible independent evaluation of a mixture of quinolone and beta-lactam. The rapid phenotypic assay may shorten the incubation times and necessary microbial mass currently required for evaluation.

Thienamycin is a carbapenem antibiotic with potent activity against gram-negative and gram-positive bacteria. Due to its promising activity but lack of chemical stability, thienamycin serves as inspiration for new synthetic antibiotic scaffolds. In this study, we report a nine-step enantioselective formal synthesis of thienamycin. Our route utilizes an asymmetric reduction, enabled by NaBH4 and D-tartaric acid, followed by a series of diastereoselective reactions to access the key azetidinone precursor to thienamycin. This azetidinone precursor could be used as an intermediate to further develop and expand the scope of next-generation beta-lactam antibiotic scaffolds.

As the most widely distributed scavenger birds on the Qinghai-Tibetan Plateau, Himalayan vultures (Gyps himalayensis) feed on the carcasses of various wild and domestic animals, facing the dual selection pressure of pathogens and antibiotics and are suitable biological sentinel species for monitoring antibiotic resistance genes (ARGs). This study used metagenomic sequencing to comparatively investigate the ARGs and mobile genetic elements (MGEs) of wild and captive Himalayan vultures. Overall, the resistome of Himalayan vultures contained 414 ARG subtypes resistant to 20 ARG types, with abundances ranging from 0.01 to 1,493.60 ppm. The most abundant resistance type was beta-lactam (175 subtypes), followed by multidrug resistance genes with 68 subtypes. Decreases in the abundance of macrolide-lincosamide-streptogramin (MLS) resistance genes were observed in the wild group compared with the zoo group. A total of 75 genera (five phyla) of bacteria were predicted to be the hosts of ARGs in Himalayan vultures, and the clinical (102 ARGs) and high-risk ARGs (35 Rank I and 56 Rank II ARGs) were also analyzed. Among these ARGs, twenty-two clinical ARGs, nine Rank I ARG subtypes, sixteen Rank II ARG subtypes were found to differ significantly between the two groups. Five types of MGEs (128 subtypes) were found in Himalayan vultures. Plasmids (62 subtypes) and transposases (44 subtypes) were found to be the main MGE types. Efflux pump and antibiotic deactivation were the main resistance mechanisms of ARGs in Himalayan vultures. Decreases in the abundance of cellular protection were identified in wild Himalayan vultures compared with the captive Himalayan vultures. Procrustes analysis and the co-occurrence networks analysis revealed different patterns of correlations among gut microbes, ARGs, and MGEs in wild and captive Himalayan vultures. This study is the first step in describing the characterization of the ARGs in the gut of Himalayan vultures and highlights the need to pay more attention to scavenging birds.