Journal of Applied Microbiology最新文献

Aims: Avian pathogenic Escherichia coli (APEC) causes colibacillosis, incurring significant economic losses. Toxin-antitoxin (TA) systems regulate bacterial virulence, biofilm formation, and antibiotic resistance. This study focuses on RatA, a toxin characterized as a ribosomal large subunit from our Tn5 transposon mutant library biofilm screen. In the clinical isolate APEC81, ratA is co-transcribed with its putative antitoxin gene, ratB, in the ratAB operon. This study aims to characterize the function of ratA in APEC and determine if ratB affects its regulation.

Methods and results: We found that deletion of ratA (ΔratA and ΔratAB) significantly impaired bacterial growth, biofilm formation, and motility, while deletion of the antitoxin gene ratB had no observable effect, indicating that RatA acts independently of RatB in modulating these traits. Further analysis identified four key active sites (V34, W103, F117, F147) essential for RatA binding to coenzyme Q. Mutating these sites recapitulated the ΔratA phenotype, confirming their functional importance.In host-pathogen interactions assays, the ΔratA mutant exhibited markedly reduced adhesion and invasion in HD-11 macrophages, diminished colonization in murine tissues, and a weakened capacity to provoke host inflammatory responses.

Conclusion: Studies demonstrate RatA as a central virulence factor in APEC, governing multiple pathogenic traits-from bacterial fitness to host interaction. These results underscore the potential of ratA as a target for anti-virulence strategies against APEC infections.

Aims: A heterotrophic nitrification-aerobic denitrification bacterial strain that could effectively remove nitrogen from wastewater was identified, and its nitrogen removal characteristics and possible mechanism underlying were investigated.

Methods and results: A nitrogen-removing strain was isolated from produced water of Changqing oilfield in the Ordos Basin and identified as Pseudomonas stutzeri 4-3 by physiological and biochemical characteristics as well as the phylogenetic analysis. Nitrification and denitrification capabilities were tested under different nitrogen sources, showing that strain 4-3 possessed heterotrophic nitrification and aerobic denitrification capabilities, with a maximum total nitrogen removal rate of 91.345%. Comparative studies under aerobic and anoxic conditions revealed that this strain effectively removed nitrogen sources, and the total nitrogen removal rates were slightly higher under aerobic conditions than those in anoxic conditions, achieving an ammonia nitrogen removal rate of 10.603 mg·L-1·h-1. The extracellular polymeric substances secreted by strain 4-3 could enhance nitrogen removal capacity, and the removal efficiency was increased by 23.5% with the increase of exogenous EPS concentration.

Conclusions: The newly isolated P. stutzeri strain 4-3 was a facultative anaerobic bacterium that carried functional genes of denitrification and exhibited efficient heterotrophic nitrification and aerobic denitrification capabilities. Moreover, EPS secreted by this strain played an auxiliary role in the denitrification process.

Aims: The purpose of this paper was to develop a dual-active topical gel combining clotrimazole (0.5%) and methyl eugenol (0.15%) and to evaluate its planktonic and antibiofilm efficacy against Candida spp., cytocompatibility, pharmaceutical performance, and benchmarking versus commercial antifungals.

Methods and results: Antimicrobial activity was measured by CLSI-adapted agar diffusion and broth microdilution against Candida albicans ATCC 10231, Candida tropicalis PNT31, and azole-tolerant Candida glabrata (ND31, ND32, 961), together with four representative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212). Biofilm inhibition was quantified in a 96-well static model using the minimum biofilm inhibitory concentration (MBIC50​-MBIC100). The gel achieved minimum inhibitory concentrations (MICs) of 125-250 µg·mL-1 and MBIC50 values 2-4 × the MICs. Compared with Canesten® and Daktarin®, MIC and MBIC50 values were consistently lower (≈30-35% lower for azole-tolerant C. glabrata isolates). Cell viability remained > 85% at MIC/MBIC50​, rheology was shear-thinning/thixotropic, and active contents were ≥ 96% retained during stability testing.

Conclusions: In vitro, the clotrimazole-methyl eugenol gel showed low MIC/MBIC50​ values (including against azole-tolerant C. glabrata), maintained cytocompatibility (>85% viability at MIC/MBIC50), and demonstrated robust pharmaceutical attributes, supporting further in vivo validation for biofilm-associated candidiasis.

Chronic wounds, including diabetic foot ulcers, venous leg ulcers, and pressure ulcers, remain a major global healthcare challenge, associated with substantial morbidity, risk of limb loss, and high healthcare costs. Increasing evidence indicates that the wound microbiome modulates inflammation, tissue repair, and responses to therapy, thereby influencing clinical outcomes. This review summarizes current knowledge on the composition and function of chronic wound microbial communities and discusses their clinical relevance as prognostic biomarkers and therapeutic targets. Microbiome structure is shaped by wound etiology, chronicity, anatomical site, and host comorbidities. Dysbiosis and biofilm formation contribute to persistent inflammation, antimicrobial tolerance, and delayed healing. Advances in sequencing and multi-omics technologies have improved microbial characterization and enabled the identification of candidate microbial signatures associated with healing trajectories. Emerging microbiome-modulating strategies such as probiotics, bacteriophages, topical oxygen approaches, and nanotechnology-based interventions show potential to shift wound ecosystems toward a pro-healing state; however, robust clinical validation remains limited. Further clinical studies are needed to validate microbiome-guided diagnostics and interventions and to establish standardized protocols for their application in clinical practice.

Aim: Bacterial vaginosis (BV) is the most common vaginal disorder in women of reproductive age. Current therapies are limited by poor activity against biofilms and high recurrence rates (>50%), demonstrating that new antimicrobials are required. Drug repurposing is an attractive approach for the discovery of new antimicrobials, so we aimed to screen repurposed libraries for activity against the key BV pathobiont Gardnerella vaginalis.

Methods and results: Two drug libraries from Medicines for Malaria Venture comprising 640 compounds were screened against G. vaginalis and various Lactobacilli species. Initial screening identified 16 G. vaginalis-selective compounds, of which 10 showed ≥90% inhibition of planktonic growth while sparing Lactobacillus crispatus. Subsequent assays revealed that three candidates displayed activity against pre-formed G. vaginalis biofilms; MMV1634360 (an antiproliferative compound with reported anticancer and antifungal activity), MMV1582487 (originally developed as an Escherichia coli aminopeptidase N inhibitor), and MMV1582497 (a thymidylate kinase inhibitor developed for Mycobacterium tuberculosis). All three produced >2-log reduction in viable cell counts at 10 µM (P < 0.05 for all compounds). Further cytotoxicity testing in VK2/E6E7 vaginal epithelial cells excluded MMV1634360 and MMV1582497 due to off-target effects, leaving MMV1582487 as a leading candidate. MMV1582487 demonstrated further activity against a high biofilm-forming G. vaginalis clinical isolate with >4log10 CFU/ml reduction in viable cell counts at 10 µM (P < 0.001), and synergy with existing antibiotic therapy.

Conclusions: We demonstrate that MMV1582487 is a selective, non-cytotoxic, anti-biofilm candidate against G. vaginalis, supporting its potential as a novel therapeutic option for BV.

Aims: Gut microbiota dysbiosis and intestinal barrier disruption are key features of metabolic disorders associated with high-fat diet (HFD) consumption. While probiotics show promise in modulating these pathways, the role of Lactiplantibacillus plantarum Q180 (LPQ), formerly Lactobacillus plantarum Q180, in restoring gut microbial balance and intestinal barrier integrity remains unclear. In this study, we aimed to investigate whether LPQ supplementation alleviated HFD-induced gut dysbiosis, intestinal barrier dysfunction, and systemic endotoxemia in a mouse model.

Methods and results: Male C57BL/6J mice received either a normal control diet or an HFD, with the latter administered with or without LPQ or resmetirom (positive control). Gut microbiota composition was assessed via 16S rRNA gene sequencing, and intestinal barrier function was assessed by fecal and serum endotoxin quantification and colonic expression of tight junction and mucin proteins. LPQ supplementation restored microbial balance, increasing short-chain fatty acid-producing genera (Lactobacillus, Bifidobacterium, Blautia, and Faecalibaculum) and reducing potentially pathogenic taxa. These microbial alterations were accompanied by decreased endotoxin levels, upregulation of epithelial tight junction genes (Zo-1, Ocln, and Claudin1), and downregulation of mucin genes (Muc2 and Muc4). Positive correlations were noted between specific commensal bacteria and barrier-related gene expression, suggesting a microbiota-linked mechanism supporting epithelial integrity.

Conclusion: LPQ attenuated HFD-induced gut microbial imbalance and intestinal barrier dysfunction, accompanied by reduced systemic endotoxemia. These findings suggest that LPQ may serve as a microbiota-targeted intervention for gut dysbiosis-related metabolic disturbances. Further studies are warranted to validate its long-term and translational potential in humans.

Aims: This study was designed to investigate the basis of atypical ampicillin/sulbactam (SAM) resistance in Salmonella isolates from raw chicken that lacked extended-spectrum or inhibitor-resistant TEM β-lactamase variants.

Methods and results: The ampicillin (AMP) minimum inhibitory concentrations (MICs) of all Salmonella isolates and blaTEM expression and copy numbers of select isolates were determined. Plasmids from select Salmonella isolates were conjugated into Escherichia coli recipients, and their AMP MICs, SAM resistance phenotypes, and blaTEM expression were quantified. SAM-resistant Salmonella isolates displayed ∼5.4-fold higher average AMP MIC and significantly elevated blaTEM expression levels compared to SAM-susceptible control. Conjugation experiments revealed differences in AMP MICs and SAM resistance phenotypes between Salmonella donors and E. coli transconjugants. An AMP MIC breakpoint of 1024 ppm ostensibly confers resistance to SAM in Salmonella.

Conclusion: Host-dependent blaTEM overexpression and resulting β-lactamase hyperproduction can lead to atypical SAM resistance in Salmonella. This study furthers our understanding of the understudied SAM resistance in Salmonella spp.

Aims: To evaluate the diversity, prevalence, and phenotypic and genotypic characteristics of carbapenem-resistant Gram-negative bacteria (CR-GNB) causing bloodstream infections, and assess the mechanisms driving their dissemination through a multi-center study in nine hospitals of Ecuador.

Methods and results: Between November 2021 and May 2022, 297 Gram-negative bacteria (GNB) were isolated from 273 patients across nine hospitals in Ecuador. Genotypic characterization of carbapenem-resistant GNB from blood cultures was performed by whole genome sequencing (WGS). CR-GNB accounted for 18.8% (56/297), predominantly Klebsiella pneumoniae (41.1%), followed by Enterobacter cloacae complex (16.1%), Acinetobacter baumannii (12.5%), and Pseudomonas aeruginosa (7.1%). CR-GNB showed high resistance to cephalosporins (80%-95%), piperacillin-tazobactam (85.7%), ampicillin-sulbactam (91.1%), and ciprofloxacin (78.6%). Genomic analysis revealed carbapenemase genes blaKPC-2 (most frequent), blaNDM-1, and blaOXA-181 across high-risk clones (e.g. K. pneumoniae ST307, ST258, ST147; A. baumannii ST1187). Carbapenemase genes were plasmid-borne (IncA/C, IncM, IncN, IncF, IncHI2, IncX3, and non-typeable) and associated with transposons (Tn4401, Tn125, and Tn3). Also, blaVIM-2 in Pseudomonas spp. was plasmid- and chromosomally encoded.

Conclusions: Our findings demonstrate a high burden of CR-GNB, primarily due to K. pneumoniae and E. cloacae complex. Furthermore, the widespread distribution of blaKPC-2, blaNDM-1, and blaOXA-181 in high-risk clones, coupled with the frequent plasmid- and transposon-mediated mobilization of these genes, highlights the crucial role of horizontal gene transfer in the dissemination of resistance.

Aims: Vaginal health is crucial to a woman's overall well-being. Bacterial vaginosis, a common gynecological condition resulting from dysbiosis, remains a significant clinical challenge. This study aims to investigate whether postbiotics derived from vaginal Lactobacillus strains exhibit therapeutic effects against bacterial vaginitis.

Methods and results: Postbiotics, consisting of inanimate microorganisms and/or their components, were analyzed and found to contain lactic acid and acetic acid as the primary acidic constituents. In a model of Gardnerella vaginalis-induced bacterial vaginosis, postbiotics demonstrated enhanced antibacterial and antioxidant activities. They significantly alleviated clinical symptoms, modulated the composition of the vaginal microbiota, and increased microbial diversity. Specifically, postbiotics reduced the abundance of endotoxin-producing Escherichia-Shigella and Enterobacteriaceae, while promoting beneficial bacteria such as Muribaculaceae, Lachnospiraceae, and Streptococcus. Additionally, postbiotic treatment restored the balance between Th17 and Treg cells and regulated associated inflammatory factors.

Conclusions: These findings indicate that postbiotics improve bacterial vaginitis through multiple mechanisms, including antibacterial and antioxidant effects, immune regulation, and restoration of vaginal flora structure and metabolic balance. This study highlights the potential clinical value of postbiotics in the treatment of bacterial vaginosis.

Aims: This study aimed to characterize a colistin- and carbapenem-resistant Pseudomonas aeruginosa ST1560 strain isolated from Guanabara Bay, Brazil, and to investigate the molecular mechanisms underlying its resistance phenotype.

Methods and results: Six surface water samples from Guanabara Bay were collected, yielding 71 P. aeruginosa subjected to antimicrobial susceptibility testing. Three isolates exhibited elevated minimal inhibitory concentrations (MICs) to colistin (≥512, 64, and 8 mg/l) in the absence of mcr genes (1-10). Among these, only strain CCVSU 5861 demonstrated carbapenemase confirmed by Blue Carba test. This strain was selected for whole-genome sequencing (Illumina). Genomic analysis identified the presence of blaKPC-2 and blaOXA-395, along with additional resistance determinants associated with aminoglycosides and fosfomycin. Genes involved in lipopolysaccharide modification, (arnA, arnT, and basS) were also detected, likely contributing to colistin resistance. The blaKPC-2 gene was located adjacent to the mobile genetic element ISKpn6, suggesting potential horizontal gene transfer.

Conclusions: The P. aeruginosa ST1560 displays a complex multidrug resistance profile, including resistance to both colistin and carbapenems. This phenotype appears to be mediated by a combination of acquired resistance genes and chromosomal mechanisms. The localization of blaKPC-2 within a mobile genetic element underscores the risk of dissemination in aquatic environments.