Antimicrobial Agents and Chemotherapy最新文献

Pneumococcal conjugate vaccines (PCVs) have significantly reduced disease burden caused by Streptococcus pneumoniae, a leading cause of childhood morbidity and mortality globally. The rise of non-vaccine serotypes is a frequent phenomenon after the use of these PCVs. This study is a national surveillance that includes all pneumococcal isolates causing invasive pneumococcal disease (IPD) (4,455 isolates) in the pediatric population to analyze the changes of strains with reduced susceptibility (IPD-RS) to different antibiotics (1,458 to penicillin/1,304 to erythromycin) and the impact of PCVs and COVID-19 pandemic on antibiotic resistance. Six periods are differentiated according to this decline: pre-PCV13, early PCV13, middle PCV13, late PCV13, COVID-19, and reopening. Between 2009 and 2023, overall IPD cases in Spain decreased by over 60% in children aged 1-4 years and by approximately 50% in infants under 1 year of age. Nevertheless, an increase in IPD-RS caused by non-PCV13 serotypes was observed, with serotype 24F being the most prevalent, which is not included in the currently licensed PCVs. The introduction of PCV13 showed a substantial impact on reducing IPD in children. The COVID-19 pandemic led to a temporary decline in the burden of disease caused by resistant strains in 2020 due to non-pharmacological measures followed by a subsequent recovery.

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.

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.

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.

High-level resistance to ceftaroline, a fifth-generation β-lactam critical for treating methicillin-resistant Staphylococcus aureus (MRSA), is an emerging threat to global health. While resistance is traditionally attributed to mecA-mediated expression of PBP2a, our study reveals a previously unrecognized mechanism. We show that high-level resistance to ceftaroline can arise independently of ceftaroline exposure through a collateral pathway triggered by carbapenems typically used to treat Gram-negative infections. Our findings reveal a two-tiered adaptive process. First, meropenem selects non-synonymous mutations in rpoB, a core transcriptional regulator, which primes resistance by reprogramming gene expression. These changes consistently co-occur with a key substitution in pbp1 (H499R), an essential protein for cell division, and specific mecA variants (Y446H, E447K) following ceftaroline exposure. Second, resistance is stabilized through regulatory and signaling adaptations, with elevated basal levels of the oxidative stress regulator Spx and its adaptor protein TrfA supporting the altered cellular state. Proteomic and biophysical studies revealed direct binding of TrfA to GdpP, the phosphodiesterase for cyclic-di-AMP, linking this regulatory circuit to elevated c-di-AMP levels and resistance maintenance. Our findings challenge the assumption that ceftaroline resistance is driven solely by PBP2a alterations and reveal how collateral resistance pathways can be activated by broad-spectrum antibiotic use. This study highlights the evolutionary capacity of MRSA to circumvent antibiotic pressure and underscores the need for improved antimicrobial stewardship.

Neisseria gonorrhoeae, the causative agent of the second-most prevalent sexually transmitted bacterial disease globally, has been classified as an urgent threat to public health and a high-priority pathogen. Concerningly, N. gonorrhoeae has developed resistance to nearly all FDA-approved drugs. Currently, no approved oral therapies exist, with parenteral administration of ceftriaxone as the only available FDA-approved treatment option for multidrug-resistant gonococcal infections. Yet, ceftriaxone-resistant isolates have now been identified globally, further highlighting the urgent need for the development of novel antibacterial agents. In a screen of 2,528 small molecules targeting G-protein-coupled receptors and related signaling pathways, ibipinabant, a potent cannabinoid receptor 1 antagonist, was identified as having the most potent anti-gonococcal activity. Ibipinabant demonstrated potent activity against a panel of 20 N. gonorrhoeae isolates, without inhibiting some representative Lactobacillus species of the vaginal microbiome. A time-kill assay revealed that ibipinabant is bactericidal, clearing the burden of N. gonorrhoeae (below the limit of detection) within 12 h. Ibipinabant was also able to clear the intracellular burden of N. gonorrhoeae inside human endocervical cells more effectively than the drug of choice, ceftriaxone. This drug was non-toxic against multiple cell lines and did not induce hemolysis of human red blood cells. Finally, in the in vivo mouse model of N. gonorrhoeae genital tract infection, ibipinabant showed a significant reduction (>95%) in the gonococcal burden after 2 days of treatment. Altogether, these results indicate that ibipinabant is a promising candidate for drug repurposing as a novel antimicrobial against multidrug-resistant N. gonorrhoeae.

Salmonella serovar Stanley ST29 is an emerging foodborne pathogen with community spread potential, while its carbapenem resistance remains uncommon. In a longitudinal pediatric case with diarrhea, two clonal ST29 isolates sampled 2 months apart revealed within-host evolutionary dynamics: Tn7051-mediated excision of bla_NDM-5 from an IncHI2/ST3 plasmid. Moreover, phylogenomics connected the case isolate to strains from a healthy carrier and from food-chain-associated sources in the same region (17-18 SNPs), underscoring community dissemination and the need for One-Health surveillance.

The treatment of invasive fungal diseases is unsatisfactory because of high morbidity and mortality despite antifungal therapy. These patients are often immunocompromised, and improvements in treatment outcome are likely to require immune therapy. To promote immune therapies against fungal diseases, the International Immunotherapy Society for Fungal Diseases was organized.

The Mycobacterium avium complex (MAC) is the primary cause of pulmonary disease (PD) among nontuberculous mycobacteria, presenting a significant treatment challenge on a global scale. A long-term (≥12 months) three-drug regimen, typically including a macrolide, such as clarithromycin (CLR) or azithromycin, along with rifampicin and ethambutol, is recommended. However, many patients fail to respond adequately to therapy, and some eventually develop macrolide resistance, making the disease even more difficult to treat. This highlights the urgent need for improved therapeutic strategies. Here, we investigated the efficacy of clofazimine (CFZ) and bedaquiline (BDQ), both repurposed from multidrug-resistant tuberculosis therapy, against macrolide-resistant MAC. In macrophage infection assays, both CFZ and BDQ showed significant intracellular inhibitory activity against macrolide-resistant clinical isolates, with CFZ generally exhibiting stronger effects. In a chronic murine model of MAC-caused progressive PD, substitution of CLR with CFZ and BDQ in the treatment regimen led to marked reductions in bacterial loads in both lung and spleen compared with the standard regimen, achieving up to 0.86 log₁₀ CFU reduction in lung and 2.17 log₁₀ CFU in spleen tissues. These findings demonstrate that CFZ and BDQ retain potent activity against macrolide-resistant MAC and highlight their potential as promising components of alternative treatment regimens.

Influenza A virus (IAV) causes annual epidemics and sporadic pandemics of acute respiratory infections resulting in significant morbidity and mortality. Although approved influenza antivirals (e.g., oseltamivir and baloxavir) exist, concerns persist about the potential for emergence of drug-resistant variants, highlighting the continuing need for new antiviral therapies. Here, we describe the development of an orally bioavailable, direct-acting antiviral (VNT-101) with a novel mechanism of action: disrupting homo-oligomerization of the influenza nucleoprotein (NP) and thereby inhibiting viral RNA synthesis. Selection of drug-resistant mutants revealed amino acid substitutions mapping to the oligomerization domain of NP, and X-ray crystallography co-structure determination of VNT-101 complexed with recombinant NP confirmed VNT-101 binding in the oligomerization pocket. Biochemical experiments using size exclusion chromatography confirmed disruption of oligomerization when this chemotype is added to preparations of recombinant NP in vitro. VNT-101 has potent and specific activity against the currently circulating IAV subtypes H1N1 and H3N2, with mean EC₅₀ values ranging from 2 to 18 nM, and displays strong efficacy in a murine model of lethal influenza infection when administered either prophylactically or therapeutically. Importantly, VNT-101 remains active against influenza variants that are resistant to either oseltamivir or baloxavir and also has potent activity against highly pathogenic avian H5N1 and H7N9 isolates that have transmitted to humans and represent strains of potential pandemic concern. These studies support the continued development of VNT-101 to augment our therapeutic arsenal against both seasonal and pandemic influenza.