Antimicrobial Agents and Chemotherapy最新文献

Temocillin, a β-lactam antibiotic, has been proposed as an alternative to carbapenems for the treatment of ESBL-producing Enterobacteriaceae. The present EUCAST breakpoints for temocillin are established based on exposure levels derived from a dosing regimen of 2 g every 8 h via intermittent infusion (II). However, the evidence supporting the efficacy of continuous infusion (CI) against ESBL-producing Klebsiella pneumoniae remains limited. The objective of the present study was to evaluate whether CI improves temocillin activity compared with II in a hollow-fiber infection model (HFIM) against CTX-M-15-producing K. pneumoniae. Four clinical isolates were characterized by whole-genome sequencing and tested for temocillin susceptibility. Mutant frequencies were estimated, and temocillin activity was assessed via time-kill assays and HFIM simulating human pharmacokinetics of temocillin 6 g/day via II and CI. Bacterial counts were performed to detect total and resistant subpopulations. Isolates showing regrowth were sequenced to identify resistance-associated mutations. The results showed that both regimens reduced bacterial burden within 8 h. However, three isolates regrew under II, while only one did under CI. CI achieved more sustained bacterial suppression and delayed or prevented the emergence of resistant subpopulations. Mutations in the cpxA gene were associated with increased temocillin MICs in regrown isolates. While both regimens demonstrated initial bactericidal activity, CI was more effective in sustaining bacterial suppression and limiting resistance emergence. These findings support the potential clinical benefit of CI for treating infections caused by CTX-M-15-producing K. pneumoniae and warrant further clinical validation.

HRS-8427, a novel siderophore cephalosporin antibiotic, is under development for treating Gram-negative infections. This study evaluated the intrapulmonary penetration and pharmacokinetic (PK) profile of HRS-8427 injection following single and multiple dose administrations in healthy Chinese subjects. A single-center, randomized, open-label Phase 1 trial enrolled 38 subjects, with 35 completing the study. In the single-dose group, subjects received a 1,500 mg intravenous infusion of HRS-8427 over 2 h. In the multiple-dose group, subjects were administered 2,000 mg of HRS-8427 intravenously every 8 h for four consecutive doses, each infused over 2 h. Bronchoalveolar lavage (BAL) was conducted to collect epithelial lining fluid (ELF) and alveolar macrophage (AM) specimens. PK analysis demonstrated a maximum plasma concentration (C_max) of 176 µg/mL and an area under the time-concentration curve from time zero to time infinity (AUC_0-∞) of 942 h·μg/mL following the single 1,500 mg dose. After multiple 2,000 mg dosing, the C_max increased to 262 µg/mlL with a corresponding AUC_0-∞ of 1,640 h·μg/mL. The ELF-to-plasma concentration ratio (C_ELF/C_plasma) exhibited a time-dependent increase, reaching 12.2% at 8 h post-final dose. Intracellular accumulation in AM remained minimal (<1%). Multiple-dose administration resulted in higher ELF exposure than single dosing. Safety assessments indicated an overall favorable tolerability profile, with most adverse events being mild in severity. Based on PK and microbiological data, a 2,000 mg regimen achieved concentrations exceeding the MIC₉₀ values of major Gram-negative pathogens, supporting further clinical development of HRS-8427 for respiratory and other Gram-negative bacterial infections.CLINICAL TRIALSThis study is registered with Chinese Clinical Trial Registry Platform as ChiCTR2300072350.

In our institution, therapeutic drug monitoring of daptomycin is performed routinely and cases of high trough concentrations have been observed in patients without known risk factors. The aim of this study was to identify risk factors of daptomycin overexposure. We performed a case-control study of daptomycin overexposure in patients who received daptomycin between 2013 and 2021. Cases and controls were defined as patients with trough concentration (Cmin) ≥60 mg/L and Cmin <60 mg/L, respectively. Univariate and multivariate analyses were performed with logistic regression models. Retained variables were further analyzed by subgroup analysis and comparison of the pharmacokinetic parameters of daptomycin. We analyzed data from 78 and 26 patients in the control and case groups, respectively. The male-to-female ratio was 1.5. The median (interquartile range) of age, body weight, and creatinine clearance was 66.5 (55-77) years, 77 (65-96) kg, and 98.5 (53-124) mL/min, respectively. Increasing body mass index (BMI) and co-administration of irbesartan were identified as risk factors of daptomycin overexposure with odds ratio (OR) (95% confidence interval [CI]) of 2.9 [1.4-6.2], and 6.1 [1.1-40.8], respectively, whereas increasing creatinine clearance was associated with decreasing risk, with OR of 0.16 [0.05-0.35]. The influence of BMI was attributed to the non-linear relationship between body weight and daptomycin PK parameters and the use of weight-based dosing in patients with high BMI. In addition to renal impairment, high BMI and irbesartan co-administration may be associated with an augmented risk of daptomycin overexposure. Dosing based on actual body weight should be avoided in obese patients.

Potentiation of existing antibiotics represents a promising strategy for combating the global health crisis of antibiotic resistance. Here we report that 1 min co-treatment with glycerol markedly enhances aminoglycoside efficacy against stationary-phase Staphylococcus aureus cells. This rapid combined treatment also effectively eliminates S. aureus biofilms and persister cells, methicillin-resistant S. aureus clinical isolates in vitro, and S. aureus in a mouse skin infection model. The potentiation is achieved through rapid enhancement of proton motive force-dependent aminoglycoside uptake. Atmospheric and room temperature plasma (ARTP)-based genome-wide mutagenesis screens further reveal the genetic basis of this potentiation, highlighting a central role for glycerol kinase (GlpK). Mechanistically, GlpK initiates glycerol catabolism and boosts cellular energy metabolism, thereby increasing proton motive force-driven aminoglycoside uptake. Unlike widely reported long-term adjuvant treatments, our approach offers an immediate potentiation strategy and may open avenues to develop glycerol as an aminoglycoside adjuvant, given its "generally recognized as safe" characteristic. Our study also illustrates the potential of ARTP-based genome-wide mutagenesis in antibiotic resistance and stress biology research.

The treatment of infections by Acinetobacter baumannii, a clinically significant nosocomial gram-negative bacterial pathogen, is hampered by antibiotic resistance, which is exacerbated by its exceptional genetic plasticity. Knowledge of the dynamics and mechanisms underlying the acquisition of antibiotic resistance is essential for the proper stewardship of their utilization. Here, we used a continuous culture device (morbidostat) to characterize the evolutionary trajectories of two A. baumannii strains in response to the increasing pressure of last-resort drugs, tigecycline and colistin. This approach allows us to confidently and comprehensively map resistance-driving mutations while circumventing both the "driver vs passenger" uncertainty and "selection bottleneck" limitations characteristic of clinical isolate analysis and conventional laboratory evolution, respectively. Tigecycline resistance predominantly occurred through the combination of missense mutations in the adeSR two-component system and disruptive events in the S-adenosyl methionine (SAM)-dependent methyltransferase, trm, while colistin resistance predominantly occurred through missense mutations in the gene cluster responsible for lipid A phosphoethanolamine modification, pmrCAB. Mapping of these mutational events over numerous publicly available A. baumannii genomes identified a relatively low prevalence of resistance to these two drugs. This work represents an initial step toward predictive resistomics of A. baumannii, leveraging gene-level genomic variations in addition to the conventional approaches based on the presence or absence of antibiotic resistance genes.

The rise of bacterial resistance has driven the exploration of novel therapies, such as bacteriophage-antibiotic cocktails (PACs), which have shown in vitro promise against resistant pathogens, including daptomycin non-susceptible-methicillin-resistant Staphylococcus aureus (DNS-MRSA) strains. While daptomycin has been a cornerstone for treating MRSA bacteremia and vancomycin-refractory infective endocarditis, the emergence of DNS-MRSA presents a significant challenge due to high morbidity, mortality, and rapid intrinsic resistance development. Phages, Intesti13 and Sb-1, were selected for their unique host range and activity against sixteen DNS-MRSA strains. Synergy with antibiotics was assessed via growth suppression curves and 24-hour time-kill assays (TKAs) across varying administration sequences and minimum inhibitory concentration (MIC) increments. Selected regimens were further assessed in an ex vivo simulated endocardial vegetation (SEV) model, with pharmacokinetic analyses confirming target antibiotic concentrations. In the ex vivo SEV model, simultaneous PAC administration using daptomycin ± phage showed superior bactericidal activity over sequential treatments in isolate C6 (P < 0.01). Similarly, in the same model, C2 reached detection limits within 48 h and remained suppressed for 120 h (P < 0.0037). Sequential outcomes varied by phage-antibiotic order and antibiotic choice. Simultaneous and phage-first regimens outperformed antibiotic-first, especially in 24 h TKAs, but showed variability at lower MICs and between in vitro and ex vivo settings. This study highlights PAC's potential for DNS-MRSA treatment, emphasizing the importance of administration timing. The observed differences across clinical strains emphasize the need for strain-specific evaluations and a deeper understanding of phage-antibiotic interactions to optimize therapy. Future research must focus on expanding phage diversity, refining protocols, and clinically validating sequential strategies to enhance PAC efficacy.

Pseudomonas aeruginosa is a leading cause of nosocomial infections, including pneumonia and urinary tract infections, and the primary cause of morbidity and mortality in cystic fibrosis patients. The emergence of multidrug-resistant strains makes these infections life-threatening. To overcome this challenge, lysocins can be employed as novel antipseudomonals. Lysocins use components of the pyocin antimicrobial system to deliver bacteriophage lysins to their peptidoglycan substrate in Pseudomonas. Peptidoglycan cleavage causes membrane destabilization, cytoplasmic leakage, and disruption of the proton motive force, thereby killing the cell. In our previous proof-of-concept study, the PyS2-GN4 lysocin killed only one-third of P. aeruginosa strains due to the targeted receptor. This limitation can now be circumvented by engineering second-generation lysocins that bind and translocate through highly conserved Pseudomonas-specific receptors. One lysocin, PyS5-I-GN4, uses a single domain from pyocin S5 to deliver the GN4 lysin through the conserved ferric pyochelin transporter, consequently killing 95% of multidrug-resistant clinical isolates tested. Importantly, PyS5-I-GN4 displayed antibiofilm properties and was bactericidal in serum and lung surfactant. Serum inactivation observed for lysins is not seen for lysocins, making this approach more effective for treating systemic Gram-negative bacterial infections. Despite its broadened pseudomonal strain coverage, PyS5-I-GN4 demonstrated narrow-spectrum antibacterial activity toward P. aeruginosa only and lacked cytotoxicity toward human cells. A single dose of lysocin was protective and reduced bacteria multiple log₁₀-fold in the lungs and secondary organs in a neutropenic murine lung infection model. These findings support lysocins as therapeutics for P. aeruginosa and provide insight into designing future constructs for other Gram-negative pathogens.

Drug tolerance allows bacteria to survive extended exposure to bactericidal drugs and is thought to play a role in drug resistance evolution. In Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), multidrug-resistant TB outbreaks are frequently caused by strains belonging to two phylogenetic lineages of the human-adapted strains of the Mtb complex, namely, lineages (L) 2 and L4. We hypothesized that members of L2 and L4 are more intrinsically drug tolerant and, as such, more readily evolve drug resistance. To explore this, we devised a high-throughput in vitro assay to measure drug tolerance in Mtb. We selected a cohort of strains representative of the globally most frequent lineages, L1-L4. We measured tolerance to rifampicin and bedaquiline and found L3 and L4 strains to have higher tolerance compared to L1 and L2 strains. In addition, phylogenetically closely related strains exhibited similar levels of tolerance, suggesting that tolerance is heritable. Finally, we explored genes previously reported to be associated with tolerance in Mtb and found significant enrichment in mutations in genes involved in cell wall and cell processes, intermediary metabolism and respiration, as well as lipid metabolism in high-tolerance strains.

Tuberculous meningitis (TBM) treatment outcomes are poor, partly due to suboptimal drug penetration into the cerebrospinal fluid (CSF). Little is known about the CSF pharmacokinetics of many TB drugs, both established and new. This study investigated the CSF penetration of cycloserine (administered as terizidone) and clofazimine, two core second-line drugs for drug-resistant tuberculosis (TB). We recruited participants with pulmonary drug-resistant TB, but without TBM, receiving terizidone and/or clofazimine for at least 2 weeks and collected serial plasma samples and a single CSF sample. Drug concentrations were quantified with validated liquid chromatography-tandem mass spectrometry methods. Pharmacokinetic parameters were determined using noncompartmental analysis, and population pharmacokinetic modeling was used to estimate the partition coefficient and equilibration half-life. Data were available from 27 participants, with a median age of 36 (range 20-60) and a weight of 52 kg (30-73 kg), who contributed 216 plasma and 27 CSF samples. The plasma pharmacokinetics of both drugs was in line with previous reports. Terizidone, measured as cycloserine, achieved CSF exposure of 69% relative to plasma, with plasma and CSF concentrations equilibrating with a half-life of 4.7 hours. Clofazimine CSF penetration was 0.13% of plasma exposure, with an equilibration half-life of 55.4 hours. Cycloserine and clofazimine concentrations in CSF approximated their estimated unbound (active) concentration in plasma, thus suggesting good penetration of the unbound drug into the CSF, supporting their potential use in TBM regimens. This study demonstrates a feasible and reproducible method for effective assessment of CSF drug penetration for CNS infections.