Journal of medical microbiology最新文献

Introduction. Klebsiella pneumoniae (Kp) is a major cause of nosocomial infections, with its evolving pathotypes including multidrug-resistant, hypervirulent (hvKp) and convergent strains posing significant diagnostic and treatment challenges due to combined antimicrobial resistance and virulence.Gap Statement. While there is a pressing requirement for thorough detection of Kp pathotypes, current assays in resource-limited environments are unable to effectively focus on essential carbapenemase and hypervirulence genes with the necessary reliability and precision.Aim. To develop and validate a multiplex PCR (m-PCR) assay capable of simultaneously detecting Kp isolates including those carrying partial or full virulence markers, alongside antimicrobial resistance.Methodology. In this study, an m-PCR assay was designed and optimized for the simultaneous detection of key biomarkers associated with hypervirulent (rmpA, rmpA2, iucA, peg344 and iroB), carbapenem-resistant (bla _NDM, bla _OXA-48-like and bla _KPC) and convergent Kp pathotypes in clinical isolates. The assay was evaluated on clinical isolates and validated against whole-genome sequencing (WGS) data for accuracy, specificity and sensitivity.Results. The developed m-PCR assay exhibited 100% specificity when compared to WGS data, successfully detecting all target genes without cross-amplification in ATCC control strains. The assay demonstrated high sensitivity, efficiently amplifying bacterial genomes from minimal DNA input as low as 1 ng µl^-1. Additionally, validation through sequencing confirmed the accuracy of detected amplicons.Conclusion. This m-PCR assay offers a rapid, sensitive and specific diagnostic tool for differentiating Kp pathotypes in clinical settings, aiding in timely intervention and improved infection control measures.

Introduction. Intestinal dysbiosis is associated with systemic health, and approaches targeting the microbiome can influence the host. Oral and intestinal microbiota are interrelated; therefore, we aimed to determine whether non-surgical periodontal treatment (NSPT) affects systemic health through its impact on the intestinal microbiota.Hypothesis/Gap Statement. Although the association between oral and gut microbiota has been suggested, there is limited evidence regarding how periodontal therapy may influence intestinal microbial composition. We hypothesized that NSPT in patients with periodontitis would lead to favourable changes in the gut microbiome, which may parallel improvements in clinical periodontal parameters.Aim. This study aimed to investigate the effect of NSPT on both oral and intestinal microbiota and to evaluate whether changes in gut microbial composition correlate with periodontal clinical outcomes.Methodology. Five systemically healthy individuals with grade C periodontitis and five systemically and periodontally healthy individuals were included. Saliva and stool samples were collected at baseline and 1 month after NSPT. DNA extractions were performed and subjected to 16S ribosomal RNA gene sequencing on the Illumina Novaseq at the V3-V4 hypervariable regions.Results. Grade C periodontitis patients displayed distinct oral and gut microbiomes compared to healthy individuals. NSPT resulted in a reduction in the diversity of both saliva and stool samples in healthy individuals (P>0.05). Salivary Fusobacteriota levels (P<0.05) and the gut Firmicutes/Bacteroides ratio decreased after NSPT. Moreover, changes in gut microbiota significantly correlated with improvements in periodontal probing depth and clinical attachment level in periodontitis patients.Conclusion. The improvement in clinical periodontal parameters after NSPT correlates with a positive shift in the gut microbiome towards health. Although the number of participants was limited, these findings support a strong relationship between periodontal and gut status. Further studies with larger cohorts and long-term follow-up are required to confirm these results.

For decades, the 'Intermediate' (I) category in antimicrobial susceptibility testing was frequently misinterpreted as indicative of therapeutic failure, rather than an opportunity for dose optimization. This misunderstanding shaped prescribing behaviour, antimicrobial trial design and guideline development. The 2019 European Committee on Antimicrobial Susceptibility Testing redefinition of the 'I' category as 'Susceptible, Increased Exposure' (SIE) highlighted the potential for treatment efficacy through dose adjustment, challenging entrenched prescribing behaviours and exposing limitations in historical trials, guidelines and surveillance practices. Antimicrobial stewardship that employs SIE-based strategies can preserve narrower-spectrum agents. However, the misapplication of 'I' can promote unnecessary broad-spectrum antimicrobial prescribing. Surveillance systems, clinical decision support and antimicrobial stewardship should be continuously updated to reflect current pharmacological principles and thereby enhance patient care outcomes.

Introduction. Cryptococcus neoformans is an opportunistic fungal pathogen that causes pulmonary cryptococcosis, or an acute or chronic infection in the lungs, and cryptococcal meningitis, an infection of the brain and spinal column, in immunocompromised individuals. Fungal infections are responsible for ~1.7 million deaths each year. In contrast to antibacterial drugs, the quantity of antifungal drugs capable of combating fungal infections remains low. With high toxicity and increased resistance to antifungals in recent years, the importance of finding new options for antifungal therapy is even more crucial.Hypothesis. We hypothesized that a series of organoantimony compounds that previously exhibited antifungal activity could serve as effective antifungal drugs.Aim. We aimed to evaluate the antifungal activity of these compounds and their mechanism of action.Methodology. We first evaluated antifungal activity via MIC and minimum fungicidal concentration assay. Next, we evaluated cytotoxicity, followed by mechanistic studies via electron microscopy and RNA sequencing studies. Finally, we evaluated activity in vivo using a Galleria mellonella model.Results. Results showed that several compounds were antifungal and also non-toxic. RNA sequencing identified several differentially regulated C. neoformans genes and pathways, including those associated with membrane transport and formation, ribosome biogenesis and gene expression. Scanning electron microscopy and transmission electron microscopy studies show altered morphology and cellular death following the treatment of C. neoformans with the compounds. Compounds had moderate efficacy in the G. mellonella infection model.Conclusion. These studies show that organoantimony compounds are promising antifungal therapies, and more studies are currently underway to improve efficacy and narrow down their mechanism(s) of antifungal activity.

Introduction. Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an emerging pathogen closely related to Streptococcus pyogenes, causing infections from mild to severe, including necrotizing fasciitis and toxic shock syndrome. Understanding bacterial diversity is crucial for monitoring the spread of antimicrobial-resistant and highly virulent strains. Clonal analysis by whole-genome sequencing (WGS) is costly, time-consuming and requires specialized bioinformatics expertise. PFGE-defined clones are often linked to human infections, but PFGE is also demanding and costly and results can vary between laboratories.Aim. This study explores the use of matrix-assisted laser desorption/ionization-time of flight MS (MALDI-TOF MS) to detect discriminatory biomarkers that discriminate SDSE strains exhibiting distinct PFGE clonal types.Methodology. MALDI-TOF MS spectra were generated from SDSE strains using a Microflex LT mass spectrometer (Bruker) and analysed with BioNumerics software v7.6. To validate the genetic relevance of PFGE pulsotypes, WGS and phylogenomic reconstruction were performed.Results. Unique MALDI-TOF MS biomarker peaks consistently differentiated SDSE strains corresponding to PFGE patterns A and B, providing robust molecular signatures for discriminating these clonal types. Phylogenomic analyses further supported this distinction by clustering PFGE A and B strains into two distinct main clades with an elevated accuracy of 95.2 (95% confidence interval: 76.2-99.9%).Conclusion. MALDI-TOF MS is effective not only for species identification but also for rapid and reliable assessment of SDSE clonal diversity. This approach has the potential to enable epidemiological tracking of specific clones, enhance understanding of SDSE in human infections and provide a practical tool for research and clinical surveillance.

Introduction. Household outbreaks of Salmonella enterica serovar Typhi (S. Typhi) typically involve genetically similar strains, often within a 0-5 single-nucleotide polymorphism (SNP) single linkage cluster. However, unusual genetic heterogeneity may indicate more complex transmission dynamics. This case represents an instance of household transmission facilitated by an asymptomatic carrier harbouring genetically diverse S. Typhi strains. A healthy adult developed severe typhoid requiring hospitalization, and two children required treatment. Public health epidemiological connections among the cases supported the findings of the phylogenetic analysis.Hypothesis/Gap Statement. We hypothesized that a household cluster of S. Typhi infections, displaying greater-than-expected genetic diversity, may have originated from a chronic carrier with a diverse in-host bacterial population - an under-recognized transmission route.Aim. To investigate the source and genomic diversity of a household cluster of S. Typhi cases with no recent travel history and to assess the role of asymptomatic carriage in transmission.Methodology. We conducted detailed contact tracing, epidemiological investigations and whole-genome sequencing on isolates from four household cases. An asymptomatic contact, with a history of S. Typhi infection and recent travel to Pakistan, underwent enhanced sampling and genomic analysis of multiple S. Typhi isolates.Results. The four household cases formed a 25-SNP single linkage cluster, inconsistent with typical isogenic clustering. Genomic analysis of multiple isolates from the asymptomatic carrier revealed a genetically diverse S. Typhi population with evidence of in-host evolution. Two case isolates were nested within the genomic diversity of the carrier's isolates. Epidemiological investigations identified no alternative sources of infection.Conclusion. This case series highlights the complexity of defining S. Typhi transmission using discrete SNP thresholds. While epidemiological links suggested a single source, phylogenetic analysis revealed notable genetic diversity among the strains. The findings underscore the public health risks posed by chronic carriers harbouring diverse S. Typhi populations and the complications associated with typhoid transmission and disease severity.

Introduction. Talaromyces marneffei (TM) is a common opportunistic infection among patients with AIDS, characterized by rapid systemic dissemination and a high mortality rate. Early identification of patients at risk of death is critical to improving clinical outcomes.Hypothesis/Gap Statement. Despite the severity of disseminated TM infection (DPSM), few predictive tools exist to assess mortality risk in affected AIDS patients. A clinical prediction model incorporating novel inflammatory markers may help guide timely intervention.Aim. This study aimed to identify independent risk factors for mortality in AIDS patients with DPSM and to develop and validate a nomogram for individualized risk prediction.Methodology. A retrospective study was conducted on 174 AIDS patients with DPSM and complete clinical data admitted to Hangzhou Xixi Hospital between January 2013 and June 2024. A training cohort of 104 patients was used to identify mortality-related risk factors via logistic regression and to construct a predictive nomogram. The remaining 70 patients constituted a validation cohort to evaluate the model using area under the curve (AUC), decision curve analysis (DCA) and calibration curves.Results. The overall mortality rate was 18.97% (33/174). Effusion, bone marrow suppression, systemic inflammation and malnutrition were significantly associated with fatal outcomes (P<0.05). Multivariate logistic regression identified white blood cell count, C-reactive protein-to-prealbumin ratio and procalcitonin-to-albumin ratio as independent risk factors for mortality. The nomogram based on these predictors showed strong discriminative power in both training and validation cohorts (AUC=0.89 and 0.78, respectively). DCA demonstrated the clinical utility and net benefit of the model.Conclusion. This study identified key predictors of mortality in AIDS patients with DPSM and developed a validated nomogram incorporating novel inflammatory markers. The tool offers potential value for individualized risk assessment and clinical decision-making.

Background. Melioidosis is a potentially life-threatening infectious disease. The diagnosis of melioidosis is time-critical due to the organism's intrinsic antimicrobial resistance and requirement for directed therapy.Aim. To assess the ability of an automated molecular diagnostic instrument to detect Burkholderia pseudomallei directly from clinical samples.Methods. Urine, sputum, swabs and Ashdown's (ASH) broth were spiked with known concentrations of B. pseudomallei and analysed using an automated PCR platform (Panther^® Fusion; Hologic) targeting the type III Secretion System (TTS-1) gene. In addition, clinical specimens from patients with confirmed melioidosis were also evaluated.Results. Urine was the clinical sample that demonstrated the lowest limit of detection (LOD), 1.8×10² c.f.u. ml^-1. Compared with dry swabs (LOD: 1.0×10³ c.f.u. ml^-1), Amies agar swabs were inferior (LOD: >3.3×10⁴ c.f.u. ml^-1). Inoculation of dry swabs into ASH, with an abbreviated incubation period, did not improve detection. All culture-positive sputum and urine samples from patients with confirmed melioidosis were detected by the PCR method.Conclusion. This study demonstrates the ability of the Panther^® to directly detect B. pseudomallei across a range of clinical sample types and estimates the minimum bacterial concentration required for diagnostic detection. The described methodology holds promise for expediting diagnosis and, in turn, enhancing patient outcomes.

Introduction. The distribution of micro-organisms in healthy organisms remains a subject of debate. Emerging evidence revealed the colonization of microbial communities in multiple anatomical sites previously considered sterile under homeostatic conditions. However, the mechanistic relationship between compromised intestinal epithelial barrier integrity and subsequent translocation of gut-resident bacteria into systemic circulation has yet to be comprehensively elucidated.Hypothesis/Gap Statement. Under intestinal leakage, gut micro-organisms can break through the intestinal barrier and then translocate to other organs.Aim. This study investigates the distribution of micro-organisms in healthy organisms to determine whether gut bacteria translocate to sterile organs only under the condition of intestinal leakage using GFP-labelled Escherichia coli (GFP-E. coli) tracing.Methodology. Female C57BL/6 mice (5 weeks old) were administered either a glacial acetic acid enema [inflammatory bowel disease (IBD) group] or a sterile normal saline enema [normal control (NC) group]. All mice were subsequently gavaged with GFP-E. coli. HE staining and Alcian blue staining were performed to evaluate the colon injury. The expression levels of intestinal tight junction proteins (ZO-1 and occludin) were tested by reverse transcription quantitative PCR and immunofluorescence staining. The distribution of GFP-E. coli in multiple organs was assessed through bacterial culture, confocal microscopy and PCR.Results. In the IBD mice, mucopolysaccharide accumulation levels (P<0.01) and tight junction proteins ZO-1 (P<0.001) and occludin (P<0.01) in the colon were significantly decreased compared with the NC group. Bacterial culture showed that there was no GFP-E. coli in the blood, heart, liver, spleen, lungs, kidneys or oviducts of normal mice, while the number of GFP-E. coli colonies in the blood (219 c.f.u. ml^-1), liver (2.39×10⁵ c.f.u. ml^-1) and lungs (2.50×10⁸ c.f.u. ml^-1) of the IBD mice was significantly higher than that of the NC group. The confocal microscopy and PCR results also showed that the number of GFP-E. coli in the liver and lungs of the IBD group was significantly higher than that of the NC group (P<0.001).Conclusion. Healthy mice maintain a sterile microenvironment in the blood, heart, liver, spleen, lungs, kidneys and oviducts. However, compromised intestinal barrier integrity facilitates microbial translocation from the intestinal lumen into the blood, liver and lungs. This study advances our understanding of endogenous infections caused by IBD, demonstrating the crucial role of intestinal permeability in bacterial infections.