Antimicrobial Agents and Chemotherapy最新文献

Colistin is considered one of the last-resort antibiotics for treating infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, the emergence and dissemination of mobile colistin resistance gene, mcr, have severely compromised the clinical utility of colistin. Combination therapy has emerged as a promising strategy to restore and enhance antibiotic efficacy against such bacterial infections. In this study, we identified broxyquinoline (BRO), an antiprotozoal compound, as a potent colistin adjuvant that significantly enhanced colistin activity against both colistin-susceptible and colistin-resistant Gram-negative bacteria by markedly reducing the minimum inhibitory concentration. Mechanistically, BRO disrupts bacterial membrane integrity, increases membrane permeability and fluidity, collapses the proton motive force, induces reactive oxygen species (ROS) accumulation, and depletes intracellular ATP, collectively disturbing bacterial homeostasis. Additionally, BRO exhibited high-affinity binding to lipopolysaccharide (LPS) and attenuated subsequent LPS-induced inflammatory responses in host cells. In murine thigh and lung infection models, the BRO-colistin combination restored colistin efficacy in vivo, evidenced by significantly reduced bacterial loads. In the lung infection model, this combination further improved survival, alleviated pulmonary pathological damage, and reduced the levels of pro-inflammatory cytokines (TNF-α, IL-1β) in bronchoalveolar lavage fluid. Collectively, these findings support the BRO-colistin combination as a promising therapeutic strategy to overcome colistin resistance and combat MDR Gram-negative infections.

Pseudomonas aeruginosa is an opportunistic human pathogen and a frequent cause of multidrug-resistant infections. This organism continues to evade antimicrobial therapy despite the clinical introduction of new antipseudomonal antibiotics over the past several years. One of these agents is cefiderocol (FDC), a novel siderophore-cephalosporin conjugate antibiotic that was designed to overcome both intrinsic and acquired β-lactam resistance mechanisms in P. aeruginosa. However, studies have demonstrated that inactivation of energy transducer protein (TonB)-dependent receptors, most notably the catechol siderophore receptor piuA, can substantially curtail the drug's ability to permeate the bacterial outer membrane, leading to rapid development of resistance. In this study, we examined the FDC resistance mechanisms of the laboratory strain PA14. We demonstrated that inactivation of the ferripyochelin receptor FptA was a first-step mutation toward FDC resistance. Through transposon mutagenesis, we identified several resistance pathways following fptA inactivation, such as the loss of an additional FDC receptor and overexpression of the MuxABC-OpmB multidrug efflux system. Introduction of clinically identified mutations analogous to these transposon insertions in the absence of fptA conferred full FDC non-susceptibility while preserving the activity of other antipseudomonal β-lactam antibiotics. We also demonstrated that inactivation of fptA in a pyoverdine biosynthetic mutant disrupted bacterial iron homeostasis and conferred a fitness disadvantage. These FDC resistance mechanisms identified in PA14 highlight the long-term challenges of using FDC treatment for drug-resistant P. aeruginosa infections.

Human norovirus (HNoV) is a major cause of gastroenteritis worldwide, for which no antiviral therapies exist to date. Previously, our lab has demonstrated that both HNoV and murine norovirus (MNV1) are highly dependent on the expression of the Ras-GTPase-activating protein-binding protein 1 (G3BP1), a cellular protein mostly involved in the assembly of stress granules. We, therefore, hypothesize that targeting G3BP1 could be a promising antiviral strategy against noroviruses. Here, we designed a proof-of-concept study to test targeted protein degradation as a mechanism to induce the specific proteolysis of G3BP1 via the proteasome. To do so, we generated a cellular platform for the overexpression of G3BP1 fused to the bacterial protein Halotag (HaloG3BP1). First, we showed that MNV1 replication is restored in G3BP1-knockout (ΔG3BP1) cells complemented with HaloG3BP1. We then used a PROteolysis TArgeting Chimera (PROTAC) directed toward the Halotag (HaloPROTAC) to induce the specific degradation of HaloG3BP1. We further demonstrate that proteolysis of G3BP1 reduces MNV1 replication, leading to a lower infectious virus yield and preventing virus-induced cell death. We also confirmed that the mechanism of HaloPROTAC3 is mediated via the recruitment of Cullin2-VHL E3-ubiquitin ligase. Our findings add to the body of evidence supporting that targeting of the cellular protein G3BP1 can be used as an antiviral approach and validates the use of PROTACs for the efficient and specific degradation of cellular factors as a feasible methodology to combat viral diseases.

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.

Resistance to ceftazidime-avibactam (CAZ-AVI) is a growing problem. This study describes the selection of CMY-219, a CMY-42 variant (G156D), conferring resistance to CAZ-AVI in an OXA-484-producing Escherichia coli ST410 after treatment. It raises concern about the risk of selection of CMY variants under CAZ-AVI exposure in ST410 and related clones, which commonly carry CMY-42, are prone to carbapenemase acquisition, and harbor modified PBP3.

The World Health Organization has flagged the rise of drug resistance in Aspergillus fumigatus as a critical concern. Elevated mutation rates in this pathogen contribute to the rapid development of resistance, complicating treatment efforts. We conducted a study on the prevalence of azole resistance among clinical A. fumigatus isolates in the Netherlands from 1994 to 2022 and identified 34 cyp51A variants. To investigate the impact of individual single-nucleotide polymorphisms (SNPs) and combinations thereof on the azole phenotype in TR₃₄-mediated resistance genotypes, we focused on novel, recent mutations and explored the effects of SNPs L98H, T289A, I364V, and G448S and the combination of the mutations TR₃₄/L98H, TR₃₄/L98H/T289A/G448S, and TR₃₄/L98H/T289A/I364V/G448S on azole affinity and susceptibility. We created the three-dimensional protein model of the Cyp51A protein with azoles, and the mutation was introduced to the wild-type cyp51A A. fumigatus strain by the CRISPR-Cas9 gene editing technique. Finally, in vitro susceptibility testing of A. fumigatus strains carrying the mutations was conducted to confirm the azole phenotypes observed in clinical isolates. The MICs of all four azoles against the mutated cyp51A strains, which harbored combination mutations, were higher than those of the wild type, with highly elevated MICs of itraconazole, voriconazole, and isavuconazole. Genotypes TR₃₄/L98H/T289A/I364V/G448S mutant showed a consistent phenotype to the clinical strains, which are highly resistant to voriconazole but susceptible to itraconazole. In this study, we show that molecular dynamics simulations of amino acid substitutions in the cyp51A gene correlate to the structure-function relationship of in vitro phenotype.

Children with invasive aspergillosis (IA) experience significant morbidity and mortality. Posaconazole is a broad-spectrum triazole antifungal agent indicated for IA treatment in adolescents and adults. A phase 2, open-label, noncomparative, multinational clinical trial in pediatric participants (2-to-<18 years old, body weight ≥10 kg) with possible, probable, or proven IA was conducted. Participants received intravenous posaconazole for ≥1 week, after which they could switch to oral posaconazole for a total treatment duration <12 weeks. Posaconazole dosing and selection of oral formulation (tablet or oral suspension [PFS]) were weight-based. The primary endpoint was safety, assessed as treatment-related adverse events (TRAE) through 14 days after treatment cessation. Global clinical response was a secondary and all-cause mortality an exploratory endpoint. PFS palatability was assessed using a 5-point scale. Thirty-one participants (proven/probable IA n = 9, possible invasive fungal disease n = 22) received ≥1 dose of posaconazole; 14 were 2 to <12 years, and 17 were 12 to <18 years old. Median treatment duration was 49 (range: 2-88) days. Seven participants (22.6%; 95% confidence interval [CI]: 9.6, 41.1) had ≥1 TRAE (grade 1 or 2, all resolved). One participant discontinued treatment due to a nonserious TRAE. Favorable global clinical response rates through weeks 6 and 12 were 67.7% (95% CI: 48.6, 83.3) and 77.4% (95% CI: 58.9, 90.4), respectively (no relapses). Day 114 all-cause mortality was 12.9%. No participants experienced problems taking PFS, and 90.0% rated PFS palatability as very good to neutral. Posaconazole was well tolerated and associated with high clinical response rates in pediatric patients with IA.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT04218851.

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.

Methicillin resistant Staphylococcus aureus (MRSA) bacteremia has a high rate of morbidity and mortality. Multiple clinical studies have demonstrated improved outcomes when MRSA bacteremia is treated with dual antibiotic therapy that includes a β-lactam antibiotic such as cefazolin. This is a paradox as MRSA should be inherently resistant to this class of antibiotics. We report on a serendipitous observation of a phenotype where MRSA became sensitive to cefazolin when cultured in a physiologic relevant media of fetal bovine serum as well as in synovial fluid. This could be observed across multiple clinical isolates. Expected resistance was maintained when cultured in Muller Hinton Broth (MHB). MRSA β-lactam antibiotic resistance is mediated by PBP2a, a penicillin-binding protein encoded by mecA. We hypothesized that this phenotype of antibiotic sensitivity in physiologic medium was based, in part, on levels of PBP2a expression and post-translational modifications of peptidoglycan wall teichoic acid (WTA). We, therefore, conducted quantitative RT-PCR analysis and Western blotting which demonstrated limited mecA expression PBP2a protein level when cultured in FBS as compared to the clinical microbiology standard MHB, respectively. Whole genome sequencing of loss of function mutants generated through serial passaging in FBS revealed that the clp family of proteins and rpo genes were involved in β-lactam resistance. Cell wall peptidoglycan analysis suggested that WTA glycosylation was altered between β-lactam resistant and sensitive MRSA phenotypes. Together, this suggests that clpP, rpoB, and WTA glycosylation are involved with the β-lactam sensitivity phenotype in MRSA and can be new potential targets for MRSA treatment.

Hematology patients are highly susceptible to severe bacterial infections, particularly those caused by multidrug-resistant (MDR) gram-negative pathogens, which are associated with significant morbidity and mortality. Eravacycline, a novel fluorocycline antibiotic, demonstrates broad-spectrum activity against MDR bacteria. This real-world study aimed to evaluate the effectiveness and safety of eravacycline in Chinese hematology patients. In this multicenter, retrospective study, hematology patients receiving ≥3 days of eravacycline between September 2023 and September 2024 were included. The outcomes included clinical response rate, microbiological response rate, and safety. Of 796 patients included, most had hematological diseases (94.6%) and recent chemotherapy or radiotherapy (80.2%). The most common infection was pneumonia (57.4%), and sputum (47.2%) was the most frequent specimen type for pathogen isolation. Among 481 patients with microbiological examination results, Klebsiella pneumoniae (30.5%) and Acinetobacter baumannii (17.4%) were predominant. The mean time to defervescence was 3.2 ± 2.1 days. The overall clinical response rate was 88.8%, with response rates of 84.0% in bloodstream infections and 87.5% in pulmonary infections. Microbiological response rate at the end of treatment was 90.7%. Eravacycline exhibited high susceptibility rates across A. baumannii (95.8%), K. pneumoniae (94.3%), and Staphylococcus aureus (100.0%). Only 2.5% of patients reported adverse events. Subgroup analysis showed that pulmonary diseases (P = 0.006), sepsis (P = 0.003), and duration ≤7 days (P < 0.001) of eravacycline 1 mg/kg/12 h were significantly associated with poorer clinical response rate at the end of treatment. Eravacycline demonstrated promising effectiveness and safety in treating infections of patients from the hematology department.