Antimicrobial Agents and Chemotherapy最新文献

HPTN 084 demonstrated the superiority of long-acting injectable cabotegravir (CAB-LA) compared with daily oral tenofovir disoproxil fumarate-emtricitabine (F/TDF) for HIV prevention in women. CAB-LA (600 mg) or placebo injections were administered 4 weeks after an initial dose (loading dose) and every 2 months (Q2M) thereafter; this is the approved regimen. Participants experienced both loading dose and Q2M delays during the trial. CAB concentrations were evaluated before a delay, at the visit associated with the delay, and the visit after a delayed injection was administered. During the blinded phase of the trial, 194 participants randomized to CAB-LA experienced at least one injection delay. Plasma CAB concentrations were maintained above the 4× protein adjusted 90% inhibitory concentration (4× PA-IC₉₀; protocol-specific threshold) for all loading dose and 98% of Q2M delays when injections were administered up to 6 weeks late. The feasibility of shifting to an every 3-month (Q3M) regimen in females was interrogated via simulation studies using a population pharmacokinetic model. Q3M injections in both CAB-naïve (with a loading dose) and previously CAB-exposed females were predicted to yield higher steady-state exposures than in males on the approved Q2M regimen. Although there is observed forgiveness following an isolated delayed CAB-LA injection and simulations suggest acceptable CAB-LA exposures in women with a 600 mg CAB-LA Q3M regimen, empirical efficacy of this regimen has not been established, and transitioning to this dosing schema is not recommended. Future pharmacokinetic bridging studies are aimed at evaluating higher dose CAB-LA formulations administered less frequently.

Clinical trials: This study is registered with ClinicalTrials.gov as NCT03164564.

Acinetobacter baumannii is globally recognized as a multi-drug-resistant pathogen of critical concern due to its capacity for horizontal gene transfer and resistance to antibiotics. Phylogenetically diverse Acinetobacter species mediate human infection, including many considered as important emerging pathogens. While globally recognized as a pathogen of concern, pathogenesis mechanisms are poorly understood. P-type type IV secretion systems (T4SSs) represent important drivers of pathogen evolution, responsible for horizontal gene transfer and secretion of proteins that mediate host-pathogen interactions, contributing to pathogen survival, antibiotic resistance, virulence, and biofilm formation. Genes encoding a P-type T4SS were previously identified on plasmids harboring the carbapenemase gene bla_NDM-1 in several clinically problematic Acinetobacter; however, their prevalence among the genus, geographical distribution, the conservation of T4SS proteins, and full capacity for resistance genes remain unclear. Using systematic analyses, we show that these plasmids belong to a group of 53 P-type T4SS-encoding plasmids in 20 established Acinetobacter species, the majority of clinical relevance, including diverse A. baumannii sequence types and one strain of Providencia rettgeri. The strains were globally distributed in 14 countries spanning five continents, and the conjugative operon's T4SS proteins were highly conserved in most plasmids. A high proportion of plasmids harbored resistance genes, with 17 different genes spanning seven drug classes. Collectively, this demonstrates that P-type T4SS-encoding plasmids are more widespread among the Acinetobacter genus than previously anticipated, including strains of both clinical and environmental importance. This research provides insight into the spread of resistance genes among Acinetobacter and highlights a group of plasmids of importance for future surveillance.

Candida auris is a pathogenic yeast of particular concern because of its ability to cause nosocomial outbreaks of invasive candidiasis (IC) and to develop resistance to all current antifungal drug classes. Most C. auris clinical isolates are resistant to fluconazole, an azole drug that is used for the treatment of IC. Azole resistance may arise from diverse mechanisms, such as mutations of the target gene (ERG11) or upregulation of efflux pumps via gain of function mutations of the transcription factors TAC1 and/or MRR1. To explore novel mechanisms of azole resistance in C. auris, we applied an in vitro evolutionary protocol to induce azole resistance in a TAC1A/TAC1B/MRR1 triple-deletion strain. Azole-resistant isolates without ERG11 mutations were further analyzed. In addition to a whole chromosome aneuploidy of chromosome 5, amino acid substitutions were recovered in the transcription factor Upc2 (N592S, L499F), the ubiquitin ligase complex consisting of Ubr2 (P708T, H1275P) and Mub1 (Y765*), and the mitochondrial protein Mrs7 (D293H). Genetic introduction of these mutations in an azole-susceptible wild-type C. auris isolate of clade IV resulted in significantly decreased azole susceptibility. Real-time reverse transcription PCR analyses were performed to assess the impact of these mutations on the expression of genes involved in azole resistance, such as ERG11, the efflux pumps CDR1 and MDR1 or the transcription factor RPN4. In conclusion, this work provides further insights in the complex and multiple pathways of azole resistance of C. auris. Further analyses would be warranted to assess their respective role in azole resistance of clinical isolates.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) are of major clinical concern. We analyzed 85 P. aeruginosa blood isolates non-susceptible to carbapenems collected during 2021-2023 from 15 medical centers in Israel. We aimed to determine the prevalence of high-risk clones, examine clonality, test antibiotic susceptibility, and assess the presence of acquired resistance genes, including carbapenemases. Whole-genome sequencing was performed using Illumina sequencing technology. Susceptibly was determined using the broth microdilution method. In the entire sample, 43.5% were high-risk clones. A main clade (27.1% of isolates) found in multiple hospitals comprised 19 isolates belonging to the high-risk ST654 clone and four closely related isolates. The isolates in this main clade harbored a broad set of resistance genes, including GES-type genes, and 91% had a mutated outer membrane protein (OprD). Isolates in the main clade were uniformly tobramycin (TOB) resistant and 83% were ceftolozane/tazobactam resistant. In the entire sample, we found high resistance to most antipseudomonal agents, including new beta-lactam/beta-lactamase inhibitor combinations. No uniform susceptibility to an antipseudomonal agent was found. Carbapenemases were carried by 9.4% of isolates (5.9% bla_GES-5 and 3.5% bla_NDM-1) and oprD was mutated in 67% of isolates. Thus, the epidemiology of CRPA is explained by a combination of clonal expansion of a dominant high-risk clade and sporadic occurrence of mutated strains. Our findings highlight the importance of susceptibility testing using a wide panel of antibiotics when CRPA is detected. Prevention measures tracking and controlling emerging high-risk clades and clones are crucial to limit the spread of CRPA.

Patients undergoing elective pelvic exenteration surgery who receive piperacillin/tazobactam as surgical prophylaxis are at risk of suboptimal intraoperative antibiotic exposure. With this work, we aimed to study the plasma pharmacokinetics of piperacillin and tazobactam in this population to provide dosing recommendations that optimize antibiotic exposure. We developed a prospective, observational, pharmacokinetic study of piperacillin/tazobactam in patients undergoing pelvic exenteration. Population pharmacokinetic analysis and Monte Carlo simulations were performed with Monolix and Simulx software. Probabilities of target attainment of different dosing regimens against the minimum inhibitory concentration (MIC) breakpoints (8 and 16 mg/L) were calculated. Twelve patients were included in the study, with a median age of 50.0 years [interquartile interval (45.3-57.5)] and a median weight of 79.0 kg (61.3-88.3). Median surgical time was 10.5 h (9.8-11.7). A two-compartment linear model best fitted piperacillin and tazobactam data (190 plasma samples). Monte Carlo simulations showed that a lower dose of 2 g/0.25 g loading dose followed by 4 g/0.5 g q8h by continuous infusion provided ≥90% probability of target attainment for MIC = 16 mg/L for most of the patients. For non-continuous infusion regimens, only the 2-hourly bolus re-dosing achieved intraoperative concentrations of piperacillin ≥16 mg/L. Patients with weights ≥ 100 kg and glomerular filtration rates ≥ 120 mL/min required 4 g/0.5 g q6h by continuous infusion after a loading dose. In conclusion, continuous infusion of lower doses of piperacillin/tazobactam is as adequate as the 2-hourly re-dosing recommended by the current guidelines for surgical prophylaxis in pelvic exenteration. Patients with higher weights and glomerular filtration rates are at greater risk of inadequate exposure.

Novel therapeutic strategies are urgently needed to combat pneumonia caused by Streptococcus pneumoniae strains resistant to standard-of-care antibiotics. Previous studies have shown that targeted stimulation of lung innate immune defenses through intranasal administration of the Toll-like receptor 5 agonist flagellin improves the treatment of pneumonia when combined with antibiotics. To promote translation to the clinic application, this study assessed the direct delivery of flagellin to the airways through nebulization using a vibrating mesh nebulizer in mice. Intranasal delivery achieved approximately 40% lung deposition of the administered flagellin dose, whereas nebulization yielded less than 1%. Despite these differences, nebulized flagellin induced transient activation of lung innate immunity characterized by cytokine/chemokine production and neutrophil infiltration into airways analogous to intranasal administration. Furthermore, inhalation by nebulization resulted in an accelerated resolution of systemic pro-inflammatory responses. Lastly, adjunct therapy combining nebulized flagellin and amoxicillin proved effective against antibiotic-resistant pneumococcal pneumonia in mice. We posit that flagellin aerosol therapy represents a safe and promising approach to address bacterial pneumonia within the context of antimicrobial resistance.

Ledaborbactam (formerly VNRX-5236), a bicyclic boronate β-lactamase inhibitor with activity against class A, C, and D β-lactamases, is under development as an orally bioavailable etzadroxil prodrug (VNRX-7145) in combination with ceftibuten for the treatment of urinary tract infections. At ceftibuten breakpoints of ≤1 mg/L (EUCAST) and ≤8 mg/L (CLSI), 92.5% and 99.0%, respectively, of 200 carbapenem-resistant Klebsiella pneumoniae isolates, predominantly K. pneumoniae carbapenemase producing, were susceptible to ceftibuten-ledaborbactam (ledaborbactam tested at a fixed concentration of 4 mg/L) compared to 4.5% and 30.5%, respectively, to ceftibuten alone.

New antibiotics are needed to treat gram-positive bacterial pathogens. MRS-2541 is a novel inhibitor of methionyl-tRNA synthetase with selective activity against gram-positive bacteria. The minimum inhibitory concentrations (MICs) against Staphylococcus aureus, Streptococcus pyogenes, and Enterococcus species range from 0.063 to 0.5 µg/mL. Given orally to mice at 50 mg/kg every 8 hours, MRS-2541 shows sustained plasma levels well above these MICs. In the mouse thigh infection model, MRS-2541 decreased methicillin-resistant Staphylococcus aureus and Streptococcus pyogenes bacterial loads to the same degree as linezolid. MRS-2541 is a promising new antibiotic for development against skin and soft tissue infections.

The resistance mechanism of Gram-negative bacteria to the siderophore antibiotic cefiderocol is primarily attributed to carbapenemase and siderophore uptake pathways; however, specific factors and their relationships remain to be fully elucidated. Here, we constructed cefiderocol-resistant Klebsiella pneumoniae (CRKP) strains carrying different carbapenemases and knocked out siderophore genes to investigate the roles of various carbapenemases and siderophores in the development of cefiderocol resistance. Antimicrobial susceptibility testing revealed that both bla_NDM and bla_KPC significantly increased the minimum inhibitory concentration (MIC) of Klebsiella pneumoniae (KP) to cefiderocol, while bla_OXA-48 showed a modest increase. Notably, KP expressing NDM exhibited a higher cefiderocol MIC compared to KP expressing KPC, although expression of NDM alone did not induce cefiderocol resistance. Laboratory evolutionary experiments demonstrated that combining pNDM with mutations in the siderophore uptake receptor gene cirA and pKPC with a mutation in the two-component system gene envZ led to KP reaching a high level of cefiderocol resistance. Although combining pOXA with mutations in the two-component system gene baeS did not induce cefiderocol resistance, it significantly reduced susceptibility. Moreover, siderophores could influence the development of cefiderocol resistance. Strains deficient in enterobactin exhibited increased susceptibility to cefiderocol, while deficiencies in yersiniabactin and salmochelin showed no significant alterations. In conclusion, carbapenemase gene expression facilitates cefiderocol resistance, but its presence alone is insufficient. Cefiderocol resistance in CRKP typically involves abnormal expression of certain genes and other factors, such as mutations in siderophore uptake receptor genes and two-component system genes. The enterobactin siderophore synthesis gene entB may also contribute to resistance.

To effectively reduce the health impact of coronavirus disease (COVID-19), it is essential to adopt comprehensive strategies to protect individuals from severe acute respiratory syndrome. In that sense, much effort has been devoted to the discovery and repurposing of effective antiviral and anti-inflammatory molecules. The endogenous peptide angiotensin-(1-7) [Ang-(1-7)] has been recently proposed as a promising anti-inflammatory agent to control respiratory infections. Liposomes also emerged as a safe and effective drug carrier system for local drug delivery to the lungs. In this context, the aim of this study was to develop a liposomal formulation of Ang-(1-7) [LAng (1-7)] and investigate its impact on animal survival as well as its antiviral and anti-inflammatory efficacies after intranasal administration in transgenic K18-hACE2 mice infected with SARS-CoV-2. The liposomal formulation was prepared by the ethanol injection method, exhibiting a mean diameter of 100 nm and a polydispersity index of 0.1. Following treatment of infected mice every 12 hours for 5 days, LAng (1-7) extended animal survival compared to the control groups that received either empty liposomes, free Ang-(1-7), or phosphate-buffered saline. Furthermore, the treatment with LAng (1-7) significantly decreased the viral load, as well as IL-6 and tumor necrosis factor levels in the lungs. Conventional treatment with remdesivir by parenteral route used as a positive control promoted similar effects, leading to improved survival rates and reduced viral load in the lungs without significant effects on IL-6 level. In conclusion, liposomal Ang-(1-7) emerges as a promising formulation to improve the treatment and decrease the severity of respiratory infections, such as COVID-19.