Antimicrobial Agents and Chemotherapy最新文献

To address limitations in tuberculosis (TB) therapy, we developed an inhalable, immunomodulating, biocompatible nanoparticle system (β-C-P) encapsulating rifampin that targets alveolar macrophage. The nanoparticle consists of a poly(lactic-co-glycolic acid) (PLGA) core, a chitosan coating, and a surface functionalized with 1,3-β-glucan for enhanced macrophage uptake and immunomodulation. We evaluated the safety, immunological effects, and efficacy of rifampin-loaded β-C-P nanoparticles delivered via oropharyngeal aspiration (OPA) in healthy mice and in a low-dose Mycobacterium tuberculosis (Mtb) BALB/c model treated weekly for 4 weeks, as well as in a low-dose Mtb C3HeB/FeJ model treated weekly for 8 weeks. In healthy mice, cell pellets isolated by bronchoalveolar lavage (BAL) showed higher pulmonary exposure (AUC) of rifampin with 20% β-C-P nanoparticles versus 5% β-C-P nanoparticles, while no rifampin was detected in the oral rifampin group. Flow cytometry revealed no significant changes in lung immune cell populations except for a transient neutrophil increase at day 21 in the 5% β-C-P group. In the Mtb BALB/c mouse model, weekly OPA administration of 5%, 10%, and 20% β-C-P nanoparticles significantly reduced lung CFU by 0.5-1.11 log₁₀, comparable to daily oral rifampin. In the Mtb C3HeB/FeJ (Kramnik) mouse model, weekly OPA administration of 10% and 20% β-C-P nanoparticles significantly reduced lung CFU, comparable to daily oral rifampin. Collectively, these findings demonstrate that weekly pulmonary nanoparticle delivery of rifampin-loaded β-C-P nanoparticles achieves sustained rifampin exposure and therapeutic efficacy comparable to daily dosing, without pulmonary toxicity or systemic immune activation. This supports the potential of long-acting inhalable formulations for simplified TB therapy.

Thermal dimorphic fungal pathogens are fungi that infect humans, often through the inhalation of asexual conidia, and which transition from hyphae to yeast in the human body. These fungi cause severe or chronic mycoses and are typically treated with azoles or amphotericin B. Ambruticin, a polyketide antifungal, shows promise as an alternative therapy. It targets hybrid histidine kinases (HHKs), which are fungal-specific proteins essential for osmoregulation and parasitic morphology and are conserved across thermal dimorphic species. Targeting HHKs suggests that ambruticin may therapeutically treat infections from multiple fungi without causing mechanism-based toxicity. We explore ambruticin's potential to effectively treat these fungal infections without major adverse effects.

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.

Neonatal doses for the off-patent antibiotics fosfomycin and flomoxef, which offer coverage against many extended-spectrum beta-lactamase (ESBL)-producing organisms, are based on limited data. We performed a pharmacokinetic (PK) and safety study of fosfomycin and flomoxef to confirm proposed neonatal dosing before further investigation in a trial (NeoSep1, ISRCTN48721236). Neonates with suspected sepsis, weighing more than 1,000 g, were sequentially enrolled into three antibiotic treatment cohorts: fosfomycin and amikacin (Cohort 1), flomoxef and amikacin (Cohort 2), and flomoxef and fosfomycin (Cohort 3), and followed for 28 days. Plasma samples were taken for PK assessment, with population PK modeling and simulations performed. Sixty-two neonates (48/62 [77%] preterm; 48/62 [77%] ≤7 days postnatal age [PNA]) received at least one dose of study antibiotics. Fosfomycin and flomoxef plasma concentrations were best described by a two-compartment and a one-compartment model, respectively, with postmenstrual age and PNA significantly influencing clearance. The probability of target attainment for fosfomycin was 100% for minimum inhibitory concentrations (MICs) of up to 8 mg/L, and for flomoxef, it was 100% for MICs of up to 0.5 mg/L. Adverse events (AEs) were common in this critically ill cohort. Thirteen (21%) neonates developed 19 trial antibiotic-related AEs (17 with grade ≤2, and 2 of grade 3), none of which required modification or discontinuation of allocated treatment. Seven neonates (11.6%) died. In this predominately preterm population, fosfomycin and flomoxef were safe, with drug exposures similar to published studies supporting the proposed doses for the larger, randomized NeoSep1 trial.This study is registered with ISRCTN48721236.

A novel fosfomycin-resistant glutathione S-transferase (FR-GST) gene, fosZ, was investigated, and its structural characteristics were characterized in Pseudomonas species. The fosZ gene was cloned and expressed in P. aeruginosa PAO1 and HS355, where it displayed reduced susceptibility to fosfomycin (8- to 64-fold) and its inhibitor sodium phosphonoformate (PPF). FosZ shares less than 70% amino acid identity with known FosA proteins. Bioinformatics analyzes revealed that fosZ was a transposable passenger gene within ISPa75, likely captured from Pseudomonas species. A total of 159 fosZ-bearing Pseudomonas strains were identified in GenBank over the past 22 years, sharing ten target site duplications (TSDs) associated with ISPa75. Among them, 34 strains were fully sequenced. ISPa75-fosZ was found on at least two chromosomes and 33 plasmids from four incompatibility groups, including the megaplasmids IncP-2 (24/33) and Inc_pJBCL41 (8/33), which also carried carbapenem and other antibiotic resistance genes. The most common TSDs were TSD6 (82/156) and TSD10 (48/156), predominantly in carbapenem-resistant P. aeruginosa of various sequence types, especially ST1076, ST1418, and ST463. Mobilization of ISPa75 between plasmid and chromosome was observed in P. aeruginosa MAS152. Structure prediction and analysis of FR-GST proteins revealed distinct features in the dimer interface loop. In the FosZ structure, an expanded K⁺-binding loop caused a deviation at residue S95, which participated in binding both fosfomycin and PPF. In conclusion, fosZ encodes a distinct FR-GST exhibiting reduced susceptibility to inhibition by PPF and has been acquired by transferable ISPa75 on multidrug-resistant megaplasmids, disseminating fosfomycin resistance in Pseudomonas species, particularly across China.

The increasing prevalence of Mycoplasma genitalium (MG) strains harboring macrolide and quinolone resistance-associated mutations (MRMs and QRMs, respectively) is a growing global concern. However, data on resistance patterns and genetic diversity in Japan remain limited. This study investigated MRMs and QRMs, genetic diversity using mgpB and MG309 typing, and their association with treatment outcome in MG strains collected in Tokyo, Japan, between 2023 and 2025. Between 2023 and 2025, 188 clinical samples from 162 MG-positive patients were analyzed. Resistance mutations in 23S rRNA, parC, and gyrA were sequenced, and molecular typing was performed. Treatment outcomes were assessed using test-of-cure results. MRMs in 23S rRNA and QRMs in parC S83I and gyrA were identified in 94.4%, 65.5%, and 22.5% of samples, respectively. Dual-class resistance (MRMs + QRMs) was found in 89.4% of strains. Phylogenetic analysis based on mgpB and MG309 typing revealed the emergence of dual-class drug-resistant clonal complexes, particularly those harboring mgpB alleles 79, 140, 161, and 184. Dual-QRMs were significantly associated with quinolone treatment failure (52.4% vs 23.5%, P = 0.016). Dual-class drug-resistant MG strains, including emerging clonal complexes, are spreading in Tokyo, Japan. These findings emphasize the need for continued molecular surveillance and prudent antimicrobial use to preserve treatment efficacy.

Aspergillus infection poses a major clinical challenge, particularly in immunocompromised individuals, with invasive diseases associated with high mortality. While Aspergillus fumigatus remains the predominant species causing human infections, recent studies highlight the growing clinical significance of lesser-known and cryptic Aspergillus species, which often exhibit reduced susceptibility to standard antifungal therapies. In this study, we analyzed 196 clinical Aspergillus isolates from 107 patients treated at the NIH Clinical Center between 2019 and 2022. A total of 38 Aspergillus species across 11 taxonomic sections were identified, with non-fumigatus and cryptic species accounting for 77.1% of all isolates. The most frequently recovered species were A. fumigatus sensu stricto (22.9%), A. sydowii (8.7%), A. calidoustus (7.1%), A. nidulans (6.6%), A. tanneri (6.1%), and A. terreus (5.6%). Species-level identification was achieved in 43% of isolates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In contrast, PCR sequencing confirmed species identity in over 88% of isolates by targeting the internal transcribed spacer (ITS) region of rDNA, 81% using the β-tubulin gene, and 68% using the calmodulin gene. The most common underlying clinical conditions among patients were bronchiectasis (35%), chronic granulomatous disease (22%), and pulmonary non-tuberculous mycobacterial infection (17%). Out of 107 patients, eight died (8/107, 7.5%); six of these deaths occurred in patients with chronic granulomatous disease (CGD) and two in patients with RAG1 deficiency. Antifungal susceptibility testing showed that olorofim had the lowest minimal inhibitory concentrations across species. In contrast, the activity of triazoles and amphotericin B was variable, particularly against A. tanneri, A. calidoustus, and A. sydowii. This study presents one of the largest species-level data sets of Aspergillus isolates to date, underscoring the diversity, pathogenic potential, and resistance profiles of non-fumigatus species. Accurate species identification plays an important role in guiding appropriate antifungal therapy and improving clinical outcomes, although further studies are needed to elucidate its direct impact on treatment decisions.

There is an urgent need for additional therapeutic solutions to treat serious bacterial infections caused by metallo-β-lactamase (MBL)-producing Klebsiella pneumoniae. Aztreonam, when partnered with ceftazidime/avibactam, has in vitro activity against most MBL-producing K. pneumoniae, but clinical outcomes may be suboptimal. The purpose of this study was to determine if aminoglycosides can enhance the pharmacodynamic activity of ceftazidime/avibactam plus aztreonam against MBL-producing K. pneumoniae. K. pneumoniae isolates harboring MBL genes (bla_NDM, bla_VIM, and bla_IMP) were evaluated in time-kill assays (n = 4 isolates) and the hollow fiber infection model (HFIM, n = 2 isolates). Clinically relevant doses of antibiotics were simulated in the HFIM, and observed antibiotic exposures represented the upper end of the expected patient plasma concentrations. Resistance was tracked during the HFIM, and confocal microscopy was used to assess cell morphology following antibiotic exposure. Both ceftazidime/avibactam + aztreonam and plazomicin were effective individually at reducing viable bacterial counts of susceptible MBL-producing K. pneumoniae, particularly in the HFIM. Combination regimens with aminoglycosides (amikacin or plazomicin) occasionally demonstrated synergy using traditional definitions based on viable colony counting, but they were able to consistently reduce bacterial turbidity and the emergence of filamentous cells that were observed during exposure to ceftazidime/avibactam + aztreonam. Combinations between ceftazidime/avibactam, aztreonam, and an aminoglycoside are a potentially promising therapeutic strategy to combat the rising threat posed by MBL-producing K. pneumoniae.

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.

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.