International Journal of Antimicrobial Agents最新文献

Introduction: Streptococcus pneumoniae does not produce β-lactamases and its reduced susceptibility to β-lactam antibiotics is predominantly caused by mutations of penicillin-binding proteins (PBPs), but mechanisms of PBP mutation-unrelated β-lactam antibiotic resistance in pneumococcal strains remain poorly characterized.

Methods: Susceptibility of S. pneumoniae ATCC49619 and its ciaR gene-knockout, -complemented, or -over-expression mutant (ΔciaR, CΔciaR, or ciaR^OE) to penicillin, cefotaxime, and imipenem was detected using E-test. Levels of pneumococcal ciaR-mRNA, five ccn-microRNAs, and six pbps-mRNAs were determined by qRT-PCR. Recombinant CiaR (rCiaR) binding to the promoters of ccn-microRNA genes was confirmed using electrophoresis mobility shift and chromatin immunoprecipitation assays. Sequence matching between the ccn-microRNAs and pbps-mRNAs were analyzed using IntaRNA software.

Results: S. pneumoniae ATCC49619 was sensitive to the three β-lactam antibiotics, but over-expression of CiaR, a response regulator protein in two-component system, caused the increase of MICs against these antibiotics. The ciaR^OE mutant exhibited the significantly increased transcription of ccn-microRNAs but notably decreased transcription of pbps-mRNAs, conversely the ΔciaR mutant displayed decreased levels of ccn-microRNAs and increasesed transcription of pbps-mRNAs. rCiaR could bind to the promoters of all ccn-microRNA genes in vitro and within cells. The three antibiotics at 1/8 minimal inhibitory concentrations caused a significant increase in the ciaR-mRNA and ccn-microRNAs. The mRNA-binding seed sequences in the five ccn-microRNAs matched all the promoter-containing sequences of pbps-mRNAs.

Conclusions: β-lactam antibiotics at low-concentrations induce PBP mutation-unrelated antibiotic resistance conversion of S. pneumoniae by decrease of PBPs through pathway of CiaR-mediated transcriptional increase of ccn-microRNAs and ccn-microRNA-dependent degradation of pbp-mRNAs.

In this study, we discovered bla_KPC-90 in ceftazidime-avibactam resistant clinical isolates of K. pneumoniae from a patient with multiple comorbidities. KPC-90 isolates had an insertion of two amino acids (Thr180_Ser181 ins Tyr Thr) compared to the wildtype KPC-2. Antimicrobial susceptibility testing of isolates with KPC-90 vs. KPC-2 showed ceftazidime-avibactam MICs of >128 vs. 1-2 mg/L, meropenem-vaborbactam MICs of 4 vs. 1 mg/L, meropenem MICs of 4-8 vs. >128 mg/L and imipenem MICs of 0.5-1 vs. 64 mg/L. Analysis of kinetic parameters of KPC-90 compared to KPC-2 showed decreased hydrolysis of carbapenems and increased IC50 of avibactam. Genetic characterization of the plasmid revealed that IS26 could mediate the intramolecular inversion, translocation and truncation of the resistance determinant region.

Bacterial persisters are a multidrug-tolerant subpopulation capable of surviving and resuscitating after lethal antibiotic treatment, leading to relapsing infections and the emergence of antibiotic resistance. We challenge the conventional wisdom of one persister population and show strong evidence that multiple persister subpopulations are within an isogenic Escherichia coli population, allowing them to survive lethal antibiotic stress. We conducted transcriptomic analyses at multiple time points with lethal ampicillin (Amp) antibiotic, and as expected, several genes were differentially expressed over time. We identified a subset of genes consistently upregulated by comparing transcription levels at different time points of Amp-treated to untreated. Some genes had previously been associated with persisters, while others were new. Subsequently, network analysis showed the gene response between networks but could not map hypothetical genes. Overexpressing seven hypothetical genes resulted in slow or no growth, indicating that high production harmed the cell. We then made single gene knockouts, which dramatically reduced persister level by ∼4-6 fold at 3 h and ∼10-15 fold at 6 h of Amp treatment. However, no significant difference in survival rates was observed at 24 h, indicating the presence of multiple persister subpopulations. Our mathematical model demonstrated a 20-fold decrease in the slow-decaying fraction in the mutant, suggesting the importance of decay kinetics in bacterial survival. These results support the existence of multiple persisters subpopulations, each characterized by distinct decay rates. Also, challenges the idea of complete dormancy, suggest the presence of intricate, multifaceted survival mechanisms, and indicate that the persister population itself is heterogeneous.

Background: Carbapenem-resistant bacteria pose a threat to public health. Characterizing the pharmacokinetics-pharmacodynamics (PKPD) of meropenem longitudinally in vivo against resistant bacteria could provide valuable information for development and translation of carbapenem-based therapies.

Objectives: To assess the time course of meropenem effects in vivo against strains with high MIC to predict PK/PD indices and expected efficacy in patients using a modelling approach.

Methods: A PKPD model was built on longitudinal bacterial count data to describe meropenem effects against six Escherichia coli and Klebsiella pneumoniae strains (MIC values 32-128 mg/L) in a 24h mouse thigh infection model. The model was used to derive PK/PD indices from simulated studies in mice and to predict the efficacy of different infusion durations with high-dose meropenem (2 g q8h/q12h for normal/reduced kidney function) in patients.

Results: Data from 592 mice were available for model development. The estimated meropenem concentration-dependent killing rate was not associated with differences in MIC. The fraction of time that unbound concentrations exceeded EC₅₀ (fT_>EC50, EC₅₀=1.01 mg/L) showed higher correlations than fT_>MIC. For all investigated strains, bacteriostasis at 24h was predicted for prolonged infusions of high-dose meropenem monotherapy in >90% of patients.

Conclusions: The developed PKPD model successfully described bacterial growth and meropenem killing over time in the thigh infection model. For the investigated strains the MIC, determined in vitro, or MIC-based PK/PD indices, did not predict in vivo response. Simulations suggested prolonged infusions of high-dose meropenem to be efficacious in patients infected by the studied strains.

Tigecycline, a last-resort antibiotic in the tetracycline class, has been effective in treating infections caused by multidrug-resistant bacteria. However, the emergence of the tigecycline resistance gene cluster tmexCD-toprJ, which encodes a resistance-nodulation-division efflux pump, has significantly limited its therapeutic effectiveness. In this study, we developed two CRISPR/Cas9-based plasmids, pCas9Kill and pCas9KillTS, to target and cleave tmexCD-toprJ gene cluster from bacterial plasmids and chromosomal integrative conjugative elements (ICEs), respectively. The pCas9Kill plasmid designed to eliminate tmexCD-toprJ from plasmids through electroporation, resulting in the resensitization of the bacteria to tigecycline. Nanopore long-read sequencing revealed that the plasmids were repaired by insertion sequences after tmexCD-toprJ removal. In contrast, the pCas9KillTS plasmid introduced via conjugation to target tmexCD-toprJ gene cluster on ICEs within the chromosome. This approach led to chromosomal cleavage and subsequent bacterial cell death. Our results demonstrate that both plasmids effectively inactivated tmexCD-toprJ, with pCas9Kill restoring tigecycline susceptibility in plasmid-bearing strains and pCas9KillTS causing targeted cell death in chromosomal ICE-harboring bacteria. This study highlights the potential of CRISPR/Cas9 systems in addressing antibiotic resistance, providing a promising strategy to combat tigecycline-resistant pathogens.

Immunization against rabies post-exposure prophylaxis (PEP) requires passive immunization with either monoclonal antibody (mAb) or blood-derived rabies immunoglobin (RIG). Currently, replacing traditional RIG with emerging mAb or mAb combinations is highly recommended due to the limited supply and potential safety risks of RIG. Here, we developed a mAb combination named CRM25 by combining two human mAbs, RM02 and RM05, at a 1:1 mass ratio. RM02 and RM05 were non-competing and non-overlapping mAbs targeting epitopes I and III, respectively. K226 and G229 were found to be the critical amino acid sites for RM02 neutralization, but the mutant I338T displayed decreased susceptibility to RM05 neutralization. Notably, CRM25 was capable of cross-neutralizing rabies virus (RABV) strains containing K226M or I338T mutations. CRM25 additionally showed an inhibitory effect on the infection of all tested common RABVs and non-RABV phylogroup I lyssaviruses. CRM25 not only exhibited neutralizing activity but also exhibited antiviral effects via Fc-mediated effector functions. Importantly, CRM25 was comparable to human RIG in terms of its capacity to protect Syrian golden hamsters from lethal RABV challenges. These findings promote more thorough research on CRM25's antiviral properties in cells and in vivo to enhance its clinical applicability and suggest that it may be a viable candidate medication for rabies PEP.

Sepsis, a leading cause of death in hospitals, can be defined as a dysregulated host inflammatory response to infection, which can lead to tissue damage, organ failure, and cardiovascular complications. Although there is no cure for sepsis, the condition is typically managed with broad-spectrum antibiotics to eliminate any potential bacterial source of infection. However, a potential side-effect of antibiotic treatment is the enhanced release of bacterial extracellular vesicles (BEVs), membrane-bound nanoparticles containing proteins and other biological molecules from their parent bacterium. Some of the Gram-negative EV cargo, including Peptidoglycan associated lipoprotein (Pal) and Outer membrane protein A (OmpA), have been shown to induce both acute and chronic inflammation in host tissue. We hypothesize that antibiotic concentration and its mechanism of action can have an effect on the amount of released BEVs, which could potentially exacerbate the host inflammatory response. In this study, we evaluated nine clinically relevant antibiotics for their effect on EV release from Escherichia coli. Several beta-lactam antibiotics caused significantly more EV release, while quinolone and aminoglycosides caused relatively less vesiculation. Further study is warranted to corroborate the correlation between an antibiotic's mechanism of action and its effect on EV release, but these results underline the importance of antibiotic choice when treating sepsis patients.

16S rRNA methyltransferases that act on residue A1408, NpmA and NpmB, confer high-level resistance to virtually all the aminoglycosides, but their reports are scarce. Analysing metagenomic projects in a One Health context, we identified in human and animal gut microbiomes from China and Canada a novel gene, npmC, that shares an identity of 91.5% with npmA, and up to 92.7% at amino acidic level. The protein encoded by this gene presents the conserved motifs required for A1408 methylation. Expression of the gene resulted in high-level of resistance to 4,5-disubstituted 2-deoxystreptamine (2-DOS) and to 4-monosubstituted 2-DOS aminoglycosides, as well as a moderate resistance to 4,6-disusbstituted 2-DOS aminoglycosides, including the last resort aminoglycoside plazomicin. Methylation at residue A1408 was further confirmed by mass spectrometry assays. The analysis of the npmC gene background revealed that its genetic context is associated to different insertion sequences that could mobilise it. Similarities in the genetic context between npmC and npmA suggest that they share a common ancestor. The immediate genetic context of this methyltransferase suggests high relationship to the Eubacteriales order. This finding enlarges the list of the true pan-aminoglycoside 16S rRNA methyltransferases, that threaten the usefulness and development of next-generation aminoglycosides.

We investigated the safety, tolerability, and pharmacokinetics of ZX-7101A tablets, a novel cap-dependent endonuclease inhibitor, in healthy participants in a first-in-human study. The single ascending dose (SAD) part included 40, 80, 160, 240, and 320 mg dose cohorts with10 participants in each dose cohort (8 participants received ZX-7101A tablets and 2 participants received placebo). The food effect (FE) part was a randomised, two-cycle, two-way crossover design, which enrolled 16 participants to receive single oral dose of 80 mg ZX-7101A tablets. ZX-7101A tablets were safe and well-tolerated in both SAD and FE studies. No participant died or experienced SAE, or withdrew prematurely. The prodrug ZX-7101A was rapidly transformed into the active ingredient ZX-7101 after single oral dose of 40 - 320 mg. The blood concentration of ZX-7101A was below the lower limit of quantification at most time points. ZX-7101 reached peak concentration about 3-4 h postdose in all dose cohorts. The elimination half-life of ZX-7101 was 83.01-125.55 h and AUC_0-24 was 1655.4 to 11483.7 h*ng/mL. The FE part showed the high-fat meal significantly affected the exposure parameters compared to the fasted condition. The C_max and AUC_0-t of ZX-7101 under fasted condition were 1.73 and 1.78 times those under fed condition, respectively. Single oral dose of 40 mg and 80 mg ZX-7101A tablets achieved sufficient ZX-7101 exposure for effectively inhibiting influenza A and B viruses and avian influenza viruses. These findings support 40 mg and 80 mg of ZX-7101A tablets as single dose regimens for use in phase II/III clinical trials. This study was registered at chinadrugtrials.org.cn (identifier: CTR20212778).