Antimicrobial Agents and Chemotherapy最新文献

Antimicrobial resistance (AMR) poses a critical and growing global health threat, directly causing millions of deaths, with China bearing a significant burden. Understanding the provincial dynamics and multifactorial one health drivers of AMR, especially amidst the transformative 2019-2023 coronavirus disease 2019 (COVID-19) pandemic, remains crucial but underexplored. This comprehensive study investigated the spatiotemporal patterns and multisectoral drivers of methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Klebsiella pneumoniae (CRKP), and carbapenem-resistant Acinetobacter baumannii (CRAB) prevalence across Chinese provinces using a robust 2019-2023 panel data set. Utilizing spatial autocorrelation (Global Moran's I) and a multimodel approach, including panel fixed-effects regression, least absolute shrinkage and selection operator, and random forest, we identified robust drivers across healthcare, agricultural, environmental, and socioeconomic domains. Significant positive spatial autocorrelation was found for CRKP (Moran's I = 0.225; P < 0.05) and CRAB (Moran's I = 0.159; P < 0.05), indicating geographical clustering, whereas MRSA exhibited no significant pattern. Pathogen-specific drivers emerged. MRSA prevalence was linked to livestock inventory and PM2.5; CRKP to healthcare expenditure and pig inventory; and CRAB to healthcare expenditure and hospital beds, alongside counterintuitive negative associations with population aging and average length of hospital stay. The direct annual effect of COVID-19 was not statistically significant. We conclude that Chinese AMR is a spatially heterogeneous challenge driven by complex one health factors. A striking "paradox of progress" suggests higher healthcare capacity correlates with dangerously increased carbapenem-resistant pathogens, emphasizing the urgent need for robust infection prevention and control. The pandemic's influence was predominantly indirect. These findings demand multisectoral, regionally tailored AMR strategies integrating healthcare, agricultural, and environmental policies for effective control.

We assessed in vitro chlorhexidine minimal inhibitory concentrations (MICs) across Klebsiella species from a hospital with widespread chlorhexidine use. Isolates underwent MIC testing and whole genome sequencing. Species showed varying resistance, with Klebsiella quasipneumoniae having the highest MICs. There was no clear link to acquired resistance, but some species had more chromosomal efflux pumps. Differences in chlorhexidine MICs between species highlight the role that biocides could have in shaping microbial populations in the hospital environment.

The Bacillus cereus group causes severe nosocomial infections. This group carries the chromosomal β-lactamases, including bla1 and BcII, which contribute to β-lactam resistance; however, the β-lactam resistance mechanisms are poorly understood. We performed genomic and phenotypic analyses of 48 clinical isolates from blood cultures and the reference strain ATCC14579 to clarify these mechanisms. Genomic analyses included species identification, multilocus sequence typing (MLST), and detection of β-lactamase genes using whole-genome sequencing. β-Lactam susceptibility testing, enzyme activity assays, and RT-qPCR of β-lactamases were performed. For this analysis, we developed a method to measure the enzyme activity of B. cereus group. The 48 isolates comprised three species (30 Bacillus mosaicus, 9 Bacillus cereus sensu stricto (s.s.), and 9 Bacillus luti) and 28 sequence types. Although all B. luti isolates lacked carbapenemase genes, they exhibited higher minimum inhibitory concentration (MIC) ranges for ampicillin and meropenem. The enzyme activity patterns were categorized as constitutive, inducible, or silent. All B. luti isolates and some B. mosaicus and B. cereus s.s. isolates displayed constitutive enzyme activity for penicillin G, whereas most B. mosaicus and B. cereus s.s. isolates displayed inducible activity, and five displayed silent activity. In the inducible group, the induced activity appeared to be accompanied by elevated penicillinase and carbapenemase expression. This is the first study to demonstrate interspecies variability within the B. cereus group regarding the presence of carbapenemase genes and β-lactam resistance profiles. These findings provide crucial insights into β-lactam resistance mechanisms in this bacterial group and provide a foundation for further research.

Clostridioides difficile, a leading cause of hospital-acquired diarrhea, exerts its virulence through two co-regulated toxins, TcdA and TcdB. Despite their pivotal roles, the discovery of inhibitors targeting their biosynthesis is underexplored. Here, we present a high-throughput screening (HTS) platform designed to identify toxin synthesis inhibitors (TSIs) that minimally impact bacterial growth. The primary screen utilized a C. difficile reporter strain expressing secreted Nano-luciferase (secNluc) under the tcdA promoter, whereby inhibition of secNluc production indicates toxin biosynthesis inhibition. Screening the Prestwick Chemical Library at 10 and 100 µM identified several compounds that reduced secNluc activity. Through counter-screening, we eliminated compounds that caused spectral interference. Orthogonal dose-response assays assessing the effectiveness of inhibiting toxin production without affecting growth identified meclizine, an antihistamine, as the primary antivirulence candidate. Meclizine was confirmed as a TSI by showing that it reduced TcdA and TcdB protein levels, the cytopathic potential of cultures, and tcdA and tcdB transcription as determined by ELISA, cell-rounding assays, and RT-qPCR, respectively. Meclizine significantly altered central carbon metabolism in C. difficile, upregulating carbohydrate transport systems and the conversion of lactate to pyruvate, while downregulating glycolytic genes. These changes were associated with intracellular accumulation of glucose and pyruvate, metabolites known to negatively impact toxin production. Taken together, our findings underscore the utility of the above HTS platform to identify anti-C. difficile TSIs, which can serve as molecular and cellular probes, as well as chemical starting points for developing novel therapeutics for C. difficile infection.

Mycobacterium abscessus, a rapidly growing nontuberculous mycobacterium, causes chronic pulmonary infections that are difficult to treat due to extensive intrinsic drug resistance. Through high-content screening of 786 FDA-approved drugs against intracellular M. abscessus in human THP-1 macrophages, we identified naftifine, an antifungal allylamine, as a novel antimycobacterial agent with dual-acting therapeutic mechanisms. Naftifine demonstrated potent activity against reference strains and multidrug-resistant clinical isolates. It showed enhanced efficacy in intracellular environments compared to axenic culture, indicating significant host-directed effects. Mechanistic investigations revealed that naftifine operates through a unique dual mechanism. It directly targets bacteria by inhibiting MmpL3 (MAB_4508), the essential mycolic acid transporter, and modulates host immunity through autophagy activation via the mTOR pathway suppression. Whole-genome sequencing of spontaneous naftifine-resistant mutants identified point mutations (S302T and V299G) in MmpL3. Complementation studies confirmed MmpL3 as the primary molecular target. Cross-resistance analysis with other MmpL3 inhibitors (BM212 and AU1235) validated this target identification. Notably, naftifine represents the first MmpL3 inhibitor demonstrated to induce autophagy, distinguishing it from other MmpL3-targeting compounds. Naftifine-induced autophagy enhanced macrophage-mediated bacterial clearance and reduced infection-associated necrosis, improving host cell survival. In vivo studies demonstrated a significant reduction of pulmonary and splenic bacterial burden with reduced lung inflammation. Furthermore, naftifine exhibited synergistic activity with β-lactam antibiotics without antagonizing other clinically used antibiotics. This is the first report demonstrating the unique combination of MmpL3 inhibition and autophagy induction by a single compound against M. abscessus, establishing naftifine as a promising dual-action therapeutic candidate for treating multidrug-resistant infections.

Cerebrospinal fluid (CSF) penetration of delafloxacin was evaluated in a murine model. Mice received a single 40 mg/kg intraperitoneal dose. Plasma and CSF samples were collected at five time points over 4 h and analyzed by ultra high-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). Pharmacokinetic parameters, including CSF penetration ratio (AUC_0-4h CSF/AUC_0-4h plasma), were determined using a non-compartmental model. The CSF penetration ratio of delafloxacin was 49%. Cmax/MIC ratios met pharmacokinetic/pharmacodynamic targets for Staphylococcus and Streptococcus spp., but not Enterobacterales.

Tuberculosis (TB) remains a leading cause of death due to an infectious agent. Adherence to long and complex TB treatments is supported by methods including directly observed therapy. The negative impact of missed drug doses on clinical outcomes is well established, highlighting both the importance of adherence support and methods to quantify the ability of a regimen to continue exerting a biologic effect during gaps in dosing known as treatment "forgiveness." To explore the value of the BALB/c relapsing mouse model of TB in evaluating treatment forgiveness, we assessed the impact of weekend dose holidays on the bactericidal efficacy, including CFU and RS ratio reduction and sterilizing efficacy, of RHZE/RH and BPaMZ. The cure/relapse data from this study, plus multiple historical studies, were used to identify a nonlinear mixed-effects Emax model that was then used to estimate time to cure 50% and derive time to cure 90% of mice (T90). The expected time-dependent bactericidal activity and reductions in RS ratio were observed for both treatments, with more rapid decreases for the BPaMZ groups. The weekend dosing holiday significantly decreased reductions in lung CFU and RS ratio earlier in RHZE/RH treatment, but no such effect was observed for BPaMZ. Similarly, the predicted T90 was significantly greater for RHZE/RH (but not BPaMZ), with weekend doses omitted. No major drug exposure difference was observed between the two dosing schedules. Our results suggest that BPaMZ is more forgiving of missed doses than RHZE/RH and demonstrate the utility of this methodology to support the evaluation of TB treatment forgiveness.

Rifampin, isoniazid, and ethambutol are the backbone of the regimen used to treat Mycobacterium kansasii-complex (MKC) lung disease. However, ethambutol pharmacokinetics/pharmacodynamics (PK/PD) studies to inform on optimal exposure target and clinical dose for MKC are lacking. We performed studies to determine ethambutol minimum inhibitory concentration (MIC), mutation frequency (3× MIC), a PK/PD study using the hollow fiber system model of MKC (HFS-MKC) using the reference ATCC#12478 strain, and Monte Carlo simulation experiments for clinical dose selection and susceptibility breakpoint. We also performed a literature search to generate ethambutol MIC distribution for MKC. First, nine studies were identified with MIC of 587 isolates, and MIC₅₀ and MIC₉₀ identified as 4 and 16 mg/L, respectively. Second, the ethambutol MIC of the ATCC strain was 8 mg/L, and the mutation frequency was 4.23 × 10^-2 CFU/mL. Third, in the HFS-MKC, ethambutol failed to kill M. kansasii below stasis (B₀), and resistance emerged rapidly. The target exposure was an AUC_0-24/MIC of 5.47 (95% confidence interval: 1.17-9.77). Fourth, Monte Carlo experiments of 10,000 virtual subjects identified doses of 1,200 and 3,000 mg to achieve or exceed target exposure in 18.21% and 58.57% of patients; and PK/PD MIC susceptibility breakpoints were determined as 2 and 4 mg/L, respectively. Doses >1,200 mg/day may have a higher likelihood of ocular toxicity. The risk of toxicity versus no microbial kill benefit in HFS-MKC suggests the need for better drugs compared to ethambutol in the treatment of MKC lung disease.

The increasing spread of antifungal-resistant dermatophytosis caused by Trichophyton indotineae has become a major public health and therapeutic concern. Consequently, antifungal susceptibility testing in routine clinical laboratories is essential for effective patient management. Itraconazole is currently the recommended treatment for these infections. However, few molecular or phenotypic tools are available to assess susceptibility to azoles. In this context, we evaluated the itraconazole and posaconazole MICs obtained using gradient concentration strips (GCS), in comparison with the EUCAST reference method. A total of 73 clinical isolates belonging to the Trichophyton mentagrophytes complex, including 64 T. indotineae isolates, were analyzed. MIC readings for both methods were performed on days 5 and 7 at partial (80%) and complete (100%) inhibition. We found that the optimal reading frame is on day 5 at 100% growth inhibition. Essential agreement within ±1 dilution (and ±2 dilutions) for the GCS method versus the EUCAST method was 65.8% (89%) for itraconazole and 57.5% (83.6%) for posaconazole. The GCS test appears to be a valuable method for susceptibility screening of T. indotineae clinical isolates, providing a practical option for routine laboratories despite essential agreement values below the ideal 90% threshold for method validation.

The spread of antibiotic resistance is a major concern in the setting of azithromycin mass drug distribution for childhood mortality. We performed long-read whole-genome sequencing and phenotypic resistance analysis on Streptococcus pneumoniae isolated from the nasopharynx of Nigerien children from communities treated with either six twice-yearly azithromycin distributions or placebo. Here, we showed that co-selection for macrolide, tetracycline, and trimethoprim-sulfamethoxazole genetic resistance was detected with repeated azithromycin mass drug distributions.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT02047981.