Antimicrobial Agents and Chemotherapy最新文献

Optimizing antibiotic exposures in hospital-acquired pneumonia (HAP) is crucial; however, dosing decisions often overlook target levels for the beta-lactamase inhibitor tazobactam (TAZ), and the impact of renal dysfunction and renal replacement therapy on TAZ pharmacokinetics (PK) remains poorly described. We developed a population PK model of TAZ using 162 plasma samples from 35 ICU patients with HAP, including those receiving continuous renal replacement therapy (CRRT). TAZ concentrations were quantified using validated LC-MS/MS methods. A one-compartment model was fit using Monolix, with clearance modeled as a function of creatinine clearance, CRRT effluent flow rate, and intermittent hemodialysis. Monte Carlo simulations assessed the probability of unbound TAZ concentrations exceeding 1, 2, or 4 mg/L for 100% of the interval between 24 and 48 h across intermittent, extended, and continuous infusion (CI) regimens, stratified by renal function and CRRT. TAZ clearance was driven by renal function and CRRT flow rate. All regimens achieved ≥90% probability of target attainment (PTA) at thresholds of 1-2 mg/L. At 4 mg/L, PTA fell below 90% in patients with creatinine clearance ≥150 mL/min for all regimens, with low-dose CI performing the worst. High-dose CI improved PTA at this higher threshold but may increase the risk of piperacillin overexposure. TAZ exposures sufficient for enzymatic beta-lactamase inhibition are generally achieved with standard dosing for lower thresholds but not for more aggressive targets (e.g., high extended-spectrum β-lactamase expression), particularly in patients with preserved or augmented renal function, who may require therapeutic drug monitoring or alternative therapy.

NDM-type metallo-β-lactamases (MBLs) are among the most widespread acquired carbapenemases in carbapenem-resistant Enterobacterales. As with other β-lactamases, allelic variability occurs among NDM-type MBLs, with almost 100 variants so far reported, differing by single or multiple amino acid substitutions or insertions, which may have implications for enzymatic activity. In this study, we report on a novel NDM variant, NDM-63, identified in a carbapenem-resistant ST147 Klebsiella pneumoniae from a surveillance rectal swab. Compared to NDM-1, NDM-63 features an original array of changes in the L3 loop, including deletion of phenylalanine at position 70 and two amino acid substitutions (G69S and A72H), due to a four-nucleotide deletion plus a nucleotide insertion in the gene region encoding the L3 loop. When expressed in Escherichia coli under isogenic conditions, NDM-63 conferred a resistance profile overall similar to NDM-1, but exhibiting a lower level of resistance to carbapenems and cefepime, while remaining susceptible to inhibition by taniborbactam. Present findings expand current knowledge on the structural plasticity of NDM-type MBLs and highlight that variability in the L3 loop, which contributes to delimitation of the active site, could also tolerate amino acid deletions without loss of enzymatic activity. A virtually identical K. pneumoniae carrying a non-functional bla_NDM allele entailing only the nucleotide insertion observed in bla_NDM-63 (which might have played a role in the evolution of bla_NDM) was also isolated from a bloodstream infection that occurred in the same patient, yielding a misleading result of molecular diagnostic testing due to the lack of enzyme activity despite the presence of the target gene.

Resistance to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus is mediated by the mecA-encoded, β-lactam-resistant transpeptidase, penicillin-binding protein 2a (PBP2a), which is capable of crosslinking peptidoglycan in the presence of β-lactam antibiotics. Here, we report that mutation of the lipoprotein signal peptidase II gene, lspA, from the lipoprotein processing pathway, significantly increased β-lactam resistance in MRSA, independent of changes in PBP2a levels or peptidoglycan composition. Exposure of MRSA to the LspA inhibitor globomycin also increased β-lactam resistance. Mutation of lgt, which encodes diacylglycerol transferase (Lgt) responsible for synthesis of the LspA substrate, did not impact β-lactam susceptibility. Furthermore, mutation of lgt in an lspA background restored β-lactam resistance to wild-type levels. These data suggest that accumulation of the LspA substrate, diacylglyceryl-lipoprotein, is associated with increased β-lactam resistance in MRSA.

Optimizing β-lactam antibiotic exposure in critically ill patients with hospital-acquired pneumonia (HAP) remains a challenge due to significant pharmacokinetic variability, particularly in the setting of renal dysfunction and replacement therapies. Continuous infusion (CI) of piperacillin/tazobactam aims to improve pharmacodynamic target attainment, though both subtherapeutic and potentially toxic concentrations have been reported in practice. We developed a population pharmacokinetic model of piperacillin using 162 plasma samples from 35 intensive care unit (ICU) patients with HAP, including those receiving continuous renal replacement therapy (CRRT). Piperacillin concentrations were quantified using a validated LC-MS method. A one-compartment model parameterized with renal and non-renal clearance was implemented in Monolix, incorporating creatinine clearance (CrCL), CRRT effluent flow rate, and intermittent hemodialysis as key covariates. Monte Carlo simulations in Simulx evaluated steady-state drug exposures following renal dose-adjusted CI regimens. Simulation showed that renally adjusted lower doses administered via CI (3-9 g/day) achieved target concentrations in 74-82% of patients with CrCL ≤75 mL/min. Higher doses (6-12 g/day) resulted in >20% of patients exceeding 96 mg/L across all renal strata. Among CRRT patients, lower doses provided a 100% probability of maintaining targeted piperacillin concentrations. In patients with supra-normal renal function (i.e., CrCL = 150 mL/min), low-dose CI regimens yielded a 6.1% probability of underexposure, compared to 2.7% with high-dose. CI PIP dosing based on CrCL results in variable exposures among ICU patients. Individualized dosing of PIP may be required to optimize efficacy and minimize toxicity in ICU patients treated with CI dosing.

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.

Ceftazidime-avibactam (CAZ-AVI), a novel antibiotic, is effective in treating infections caused by carbapenem-resistant Gram-negative bacteria. However, in patients receiving continuous renal replacement therapy (CRRT), both the pharmacokinetics (PK) and pharmacodynamics (PD) of the drugs can be significantly altered. Currently, there remains a lack of clear guidelines regarding optimal dosing regimens for CAZ-AVI during CRRT. Prospectively, this study evaluated the PK/PD of CAZ-AVI in 21 critically ill patients receiving CRRT. We collected blood samples at 5-7 sampling points within one administration cycle and then determined the total plasma drug concentrations. Phoenix was used to calculate the PK parameters. The clearance at steady state (CL_SS) of patients receiving CRRT was significantly reduced, and drug exposure was also significantly increased compared to healthy subjects. Notably, four patients demonstrated the free minimum plasma concentrations (fC_min) of CAZ exceeding eight times the MIC, and 90.48% (19 cases) of the patients exhibited CAZ plasma concentrations exceeding the neurotoxicity threshold of 104 mg/L. PK/PD analysis indicated that the standard dosing regimen of 2.5 g every 8 hours of CAZ-AVI may pose a risk of excessive drug exposure. In addition, CRRT was the primary elimination pathway for CAZ-AVI in critically ill patients with acute kidney injury receiving CRRT. Significant differences in extracorporeal clearance were observed between continuous veno-venous hemodialysis (CVVHD) and continuous veno-venous hemofiltration (CVVH) for both CAZ and AVI; CVVH demonstrated higher clearance for CAZ and AVI compared to CVVHD. To prevent potential toxic reactions, it is urgent to establish a safer and more rational dosing regimen for patients receiving CRRT.

Ertapenem combination therapy has been shown to expedite the time to blood culture sterilization among patients with MSSA bacteremia. The purpose of this study was to define what proportion of patients sterilizes blood cultures within 72 h of ertapenem combination treatment initiation. This was a retrospective, multicenter study of patients who received ertapenem combination therapy for MSSA bacteremia. Patients were considered to have rapid blood culture sterilization if blood cultures were negative within 72 h of ertapenem initiation and delayed blood culture sterilization if blood cultures remained positive after 72 h of ertapenem initiation. Of the 304 patients with MSSA bacteremia who received ertapenem for combination treatment, 197 met the inclusion criteria. The median (IQR) time to ertapenem initiation from the time of blood culture obtainment was 4 (3-5) days, and 47% (93/197) had definitive endocarditis. Overall, 85% (167/197) had rapid blood culture sterilization. Patients who had delayed blood culture sterilization had a trend toward a higher Pitt Bacteremia Score at the time of blood culture obtainment (2 [0-4] vs 1 [0-2], P = 0.091) and were more likely to have an oxacillin minimum inhibitory concentration of ≥0.5 µg/mL (67% vs 43%, P = 0.015) compared to those with rapid blood culture sterilization. In this large study of patients who received ertapenem combination therapy for MSSA bacteremia, 85% of patients sterilized their blood cultures within 72 h of treatment. These results suggest that a standard 3-day ertapenem course could be a reasonable stewardship strategy for patients initiated on combination therapy for MSSA bacteremia.

The escalating threat posed by multidrug-resistant (MDR) Gram-negative "superbugs" has intensified. Short antimicrobial peptides (SAMPs) have emerged as promising therapeutics with sustained potency and cost-effectiveness against drug-resistant infections. Here, we report a family of 15-residue SAMPs derived through modifying related amino acids of Kassporin-KS1 (FA), utilizing database-filtering technology to identify the most probable structural parameters related to Gram-negative bacteria. Most SAMPs exhibit sub-μM antimicrobial activity with reliable stability and low toxicity. Notably, KR and RK demonstrate significant efficacy in combating biofilms and sepsis infections in vivo. Furthermore, the acquisition of resistance by strains to SAMPs was not observed, primarily due to the multimodal antimicrobial mechanisms of SAMPs. We revealed that the multimodal mechanisms of SAMPs encompass unregulated membrane destabilization, induction of apoptotic-like death pathway, and interference with normal physiological processes. Overall, the rational design strategies proposed herein can be implemented to develop potent antimicrobial agents targeting MDR bacteria.

The gut environment includes an abundance of chemicals emanating from the host and the microbiota. To colonize animals, Salmonella uses gut chemicals as locational cues to ensure expression of energy-intensive virulence factors only when their production is necessary. cis-2-hexadecenoic acid (c2HDA), a member of the diffusible signal factor family of quorum-sensing signals, potently represses virulence-gene expression by Salmonella. Here, we report the construction and use of a recombinant bacteriophage that can establish lysogeny within Salmonella and induce it to produce c2HDA, thus repressing functions essential to its own virulence. We engineered the temperate phage P22 to favor lysogeny through transposon mutagenesis of the sieB-esc region and caused it to produce c2HDA by introduction of rpfF of Cronobacter turicensis, encoding the dehydratase/thioesterase required for c2HDA synthesis. We found that Salmonella harboring the lysogenic phage carrying rpfF produced c2HDA and repressed invasion-gene expression both endogenously and exogenously through secretion into the surrounding medium. Consequently, this phage reduced Salmonella invasion of epithelial cells by over 100-fold. We further found that both wild-type and c2HDA-producing phage administered orally to mice reduced Salmonella colonization of the gut, but that the phage carrying rpfF reduced gut inflammation more than did the phage without this gene. Collectively, our data show that a recombinant phage can be used as the vehicle for cytoplasmic delivery of c2HDA, thus providing a targeted means to manipulate Salmonella colonization of the gut.