Journal of medical microbiology最新文献

Introduction. Strongyloides stercoralis, the human threadworm, is a parasitic nematode with global distribution, estimated to infect over 600 million people. Chronic infection is often asymptomatic, but hyperinfection and dissemination syndromes can occur in the immunosuppressed with high case fatality rates. Whilst strongyloidiasis is endemic in Fiji, its prevalence in Fijian migrant groups in the UK is unknown.Gap Statement. No previous studies have been conducted on the prevalence of Strongyloides and other gastrointestinal parasites (GIPs) in Fijian migrants to the UK.Aim. We conducted a cross-sectional study of the prevalence of GIPs in a Fijian migrant population.Methodology. Participants completed a questionnaire on residence, travel and clinical symptoms and were asked to provide a serum sample for S. stercoralis IgG ELISA, venous blood samples for eosinophil count and a faecal sample for charcoal culture, multiplex real-time PCR (rtPCR) and microscopy after formalin-ethyl acetate concentration. Sequencing was performed on pooled Strongyloides larvae for nuclear 18S rRNA hyper-variable regions (HVRs) I and IV.Results. A total of 250 participants (94% male) with median (range) age 37 (20-51) years entered the study, 15 (1-24) years since leaving Fiji. S. stercoralis IgG ELISA was positive in 87/248 (35.1 %) and 14/74 (18.9 %) had a GIP detected in faeces. This included 7/74 (9.5 %) with Strongyloides and 5/74 (6.8 %) with hookworms. Dermatological symptoms were more common in those with Strongyloides, and eosinophilia (>0.5×10⁹ cells per litre) was present in 55.6% of those with positive S. stercoralis IgG. rtPCR was the most sensitive faecal diagnostic test for Strongyloides and hookworms in faeces. Sequences of nuclear 18S rRNA for HVRs I and IV confirmed the presence of S. stercoralis.Conclusion. This first cross-sectional study in Fijian migrants found a high rate of chronic infection with GIPs, particularly S. stercoralis. Faecal microscopy was insensitive compared to charcoal culture, rtPCR or serology, demonstrating the importance of specialist parasitological tests when investigating people with a suspected chronic infection. Our study highlights an overlooked burden of strongyloidiasis in the UK and has implications for screening and treatment programmes in Fiji and for migrants from Fiji.

Introduction. Mucormycosis is an aggressive, angioinvasive infection associated with high morbidity and mortality. The disease remains difficult to treat, with limited available antifungal drugs. Consequently, there is an urgent need to develop alternate therapeutics against mucormycosis. In an earlier study, we demonstrated that the non-steroidal anti-inflammatory drug diflunisal impacted the actin cytoskeleton and quorum sensing and inhibited the formation of filopodia-/cytoneme-like extensions in Rhizopus arrhizus.Hypothesis. The non-steroidal anti-inflammatory drug diflunisal could exhibit potential antifungal activity.Aim. This study aimed to investigate the plausible antifungal activity of diflunisal against a range of medically important Mucorales and its combination effect with antifungal drugs.Methodology. The antifungal activity of diflunisal against Rhizopus arrhizus, Lichtheimia corymbifera, Rhizomucor pusillus, Cunninghamella bertholletiae, Mucor indicus, Mucor irregularis and Apophysomyces elegans was evaluated by broth microdilution assay. Allied salicylates were also screened. A combination assay with amphotericin B deoxycholate and posaconazole was performed by fractional inhibitory concentration test.Results. Exposure to diflunisal inhibited Rhizopus arrhizus spore germination in a dose-dependent manner. MICs of diflunisal against different Mucorales ranged from 64 to 2048 µg ml^-1. Remarkably low levels of diflunisal (0.03-2 µg ml^-1), depending on the strain/species tested, improved the antifungal activity of amphotericin B against mucoralean fungi by twofold (ΣFIC ≈ 0.5-0.508; P<0.01). Field-emission scanning electron micrographs further confirmed these observations. MICs of posaconazole were unchanged by this compound.Conclusion. Considering that amphotericin B remains the first-line drug against mucormycosis and exhibits dose-dependent side effects in clinical practice, especially nephrotoxicity, the observed additive interaction at remarkably low, clinically achievable levels of diflunisal demonstrates its potential utility as an adjunct therapy against mucoralean fungi.

Introduction. The existence of a mutual relationship between gut microbiota and immune homeostasis highlights its importance in the context of kidney transplantation.Gap statement. The translational utility of gut microbiota as a biomarker for allograft injury has not been assessed before.Aim. In this study, we aimed to characterize the gut microbial diversity in kidney transplant recipients and investigate the alterations in the gut microbial composition in association with allograft injury such as histopathological graft rejection and calcineurin inhibitor toxicity. In addition, we compared the gut microbial quantitation using 16S metagenomics and quantitative PCR (qPCR) to assess its translational utility.Methodology. In this prospective longitudinal cohort study, we enrolled 38 kidney transplant recipients and collected serial faecal specimens (n=114), once before the induction therapy, and twice after transplant, during the first and third month. We characterized the gut microbial composition through 16S rRNA sequencing and qPCR from the DNA isolates of the samples. The recipients were clinically followed up for a median of 600 days post-transplant. Histopathological evidence of allograft rejection and calcineurin inhibitor toxicity were used for the correlational analysis with gut microbial diversity.Results. Significant differences in the gut microbial diversity were observed between the pre- and post-transplant samples. Pre-transplant gut microbiota revealed a higher relative abundance of phylum Bacteroidetes in the allograft rejection group, and a higher relative abundance of phylum Firmicutes was observed in the histopathological features of calcineurin inhibitor toxicity (hCNI toxicity) group. We found a high concordance between 16S metagenomics and qPCR outputs for assessing the gut microbial diversity. Furthermore, the receiver operating characteristic curve analysis has also proven that the pre-transplant levels of gut microbial dysbiosis, as a potential predictive biomarker for allograft injury.Conclusion. Our pilot study found a strong statistical association of gut microbial dysbiosis with kidney allograft injury, highlighting the potential of gut microbiota as a predictive biomarker and that qPCR serves as a more reliable and economic tool for assessing dysbiosis paving the way for its translational utility.

Introduction. Alcohol dependence (AD) and sleep disturbance (SD) independently affect gut microbiota, potentially disrupting the circadian rhythm of the microbiota and the host. However, the impact of SD on the composition and rhythmicity of gut flora in AD patients remains poorly understood.Gap Statement. Characteristics of gut flora and diurnal oscillations in AD patients experiencing SD are unknown.Aim. This study aims to explore alterations in gut flora and diurnal oscillations in AD patients experiencing SD.Methodology. Thirty-two AD patients and 20 healthy subjects participated, providing faecal samples at 7 : 00 AM, 11 : 00 AM, 3 : 00 PM and 7 : 00 PM for gut microbiota analysis using 16S rDNA sequencing. AD patients were further categorized into those with poor sleep (ADwPS) and those with good sleep (ADwGS) for further analyses.Results. The ADwPS group demonstrated elevated levels of anxiety, depression and withdrawal severity compared to the ADwGS group (all P<0.05). The β-diversity of gut microbiota in the ADwPS group differed from that in the ADwGS group (P<0.05). Bacterial abundances at various taxonomic levels, including Cyanobacteria and Pseudomonadales, differed between the ADwPS and ADwGS groups (all P<0.05). Utilizing unweighted UniFrac analysis, the β-diversity of gut microbiota in the ADwPS group demonstrated robust diurnal oscillation (P<0.05), whereas this pattern was statistically insignificant in the ADwGS group. Notably, the abundance of pathogenic bacteria like Pseudomonadales and Pseudomonadaceae exhibited marked diurnal fluctuation in the ADwPS group (all P<0.05).Conclusion. SD in AD patients extends beyond alcohol-induced alterations, impacting gut microbiota composition, function and diurnal oscillation patterns. This highlights its add-on influence, supplementing AD-related changes.

Introduction. Antibiotic tolerance corresponds to the bacterial ability to survive a transient exposure to antibiotics and is often associated with treatment failure. Current methods of identifying tolerance based on bacterial growth are time-consuming. This study explores the use of a growth-independent method utilizing nanomotion technology to detect antibiotic-tolerant bacteria.Hypothesis. The nanomotion signal obtained from a nanomechanical sensor measures real-time metabolic activity and cellular processes and could provide valuable information about the tolerance of bacteria to antibiotics that cannot be detected by standard antibiotic susceptibility tests.Aim. The aim of this study is to investigate the potential of nanomotion technology to record antibiotic-tolerant bacteria.Methodology. We generated a slow-growing Escherichia coli strain by manipulating mazF expression levels and confirmed its viability by several standard methods. We subsequently measured its nanomotion and the nanomotion of the WT E. coli in the presence or absence of antibiotics. Supervised machine learning was employed to distinguish slow-growing from exponentially growing bacteria. Observations for bacterial nanomotions were confirmed by standard kill curves.Results. We distinguished slow-growing from exponentially growing bacteria using specific features from the nanomotion signal. Furthermore, the exposition of both growth phenotypes to polymyxin decreased the nanomotion signal indicating cell death. Similarly, when exponentially growing cells were exposed to ampicillin, an antibiotic whose efficacy depends on the growth rate, the nanomotion signal also decreased. In contrast, the nanomotion signal remained unchanged for slow-growing bacteria upon exposure to ampicillin. In addition, antibiotic exposure can cause bacterial elongation, in which the biomass of a cell increases without cell division. By overexpressing sulA, we mimicked antibiotic-induced elongation. Differences in the nanomotion signal were observed when comparing elongating and non-elongating phenotypes.Conclusion. This work shows that nanomotion signals entail information about the reaction to antibiotics that standard MIC-based antibiotic susceptibility tests cannot detect. In the future, nanomotion-based antibiotic tolerance tests could be developed for clinical use in chronic or relapsing infections.

Aim. Melanized fungi were rarely studied for their antifungal resistance (AFR) or clinical outcome, despite rising incidence of melanized fungal ocular infections and AFR in general. We report the antifungal resistance patterns, clinical outcome and clinico-microbiological correlation in two commonly isolated melanized fungi from ocular infections, Curvularia lunata and Lasiodiplodia theobromae, at a tertiary eyecare centre in South India.Gap statement. Despite melanized fungi accounting for a significant proportion of ocular fungal infections in the Indian subcontinent, and despite there being a limited selection of effective antifungal agents available for these infections, the existing data and studies on these issues remain sparse. Therefore, this study aimed to investigate the prevalence of antifungal resistance in two of the most common melanized fungal pathogens in ocular infections, Curvularia lunata and Lasiodiplodia theobromae and correlate it with the treatment given and the clinical outcome in patients.Methodology. Electronic medical records provided the clinical data. Standard broth microdilution was performed for antifungal susceptibility testing (AFST) in 30 isolates (17 C. lunata and 13 L. theobromae) for amphotericin B and natamycin (polyenes): voriconazole, ketoconazole, posaconazole, itraconazole and fluconazole (azoles) and caspofungin (echinocandin). Multidrug resistance (MDR) was defined as resistance to more than or equal to two classes of antifungals. DNA sequencing was performed for the isolates for species confirmation. The multivariate analysis was done for determining poor prognostic factors.Results. AFST showed highest susceptibility of study isolates for voriconazole (83.3% isolates), followed by natamycin (80%), fluconazole (80%), itraconazole (76.7%), ketoconazole (70%), posaconazole (66.7%), caspofungin (66.7%) and lastly amphotericin B (63.3%). All patients empirically received topical natamycin; additional oral ketoconazole/intraocular voriconazole was administered in select few. MDR was strongly associated with poor clinical outcome (multivariate analysis: P = 0.03, odds ratio = 7.8). All patients had microbial keratitis, one progressed to endophthalmitis. Additionally, therapeutic penetrating keratoplasty was required in 40% of cases. Globe salvage was possible in 80% patients, though good visual outcome was seen in only half of them. Both, anatomical and visual outcomes, were poor in 20% of patients. DNA sequencing showed C. lunata as the highest study species.Conclusion. C. lunata and L. theobromae showed varying in vitro antifungal susceptibility and clinical outcome in ocular infections. Voriconazole had significantly higher activity, while amphotericin B had lower activity in vitro for these melanized fungi. MDR isolates showed poorer clinical outcome.

Introduction. Shiga toxin-producing Escherichia coli (STEC) are zoonotic, gastrointestinal pathogens characterized by the presence of the Shiga toxin (stx) gene. Historically, STEC O157:H7 clonal complex (CC) 11 has been the most clinically significant serotype; however, recently there has been an increase in non-O157 STEC serotypes, including STEC O103:H2 belonging to CC17.Gap statement. STEC O103:H2 is an STEC serotype frequently isolated in England, although little is known about the epidemiology, clinical significance, associated public health burden or evolutionary context of this strain.Aim. Surveillance data and whole-genome sequencing data were analysed to determine the microbiological characteristics and public health burden of CC17, including the clinically significant serotype O103:H2, in England and Wales.Methodology. Isolates of E. coli belonging to CC17 (n=425) submitted to the Gastrointestinal Bacteria Reference Unit from 2014 to 2022 were whole genome sequenced, integrated with enhanced surveillance questionnaire data and analysed retrospectively.Results. Overall, diagnoses of CC17 infection increased every year since 2014. Most cases were female (58.5%), with the highest proportion of cases belonging to the 0-4 age group (n=83/424, 19.6%). Clinical presentation data identified diarrhoea (92.1%), abdominal pain (72.4%) and blood in stool (55.3%) as the most frequent symptoms, while 20.4% cases were admitted to hospital and 1.3% developed haemolytic uraemic syndrome. The five most common established serotypes were O103:H2 (64.5%), O123:H2 (11.1%), O151:H2 (6.6%), O71:H2 (3.3%) and O4:H2 (2.6%). The majority of CC17 isolates (78.6%) had the stx1a/eae virulence gene combination. Nine outbreak clusters of STEC infections that were mainly geographically dispersed and temporally related were identified and associated with foodborne transmission.Conclusions. Nationwide implementation of PCR to detect non-O157 STEC and improvements to algorithms for the follow-up of PCR-positive faecal specimens is recommended. Enhanced surveillance is necessary to assess the incidence of CC17 infection and overall burden of this CC within the UK population.

Background. Commensal streptococci are common inhabitants of the oral microbiome and regulate its structure and function in beneficial ways for human health. They can, however, also be opportunistic pathogens and act as a reservoir of resistance genes that can be passed on to other bacteria, including pathogens. Little is known about the prevalence of these commensals in parents and their children and their antimicrobial susceptibilities in the Belgian general population.Gap Statement. The macrolide susceptibility of commensal oral Streptococci in Belgium is unknown.Methods. We assessed the prevalence and azithromycin susceptibility of commensal streptococcal species in the parents (n=38) and children (n=50) of 35 families in Belgium.Results. The most frequently detected taxonomic grouping was Streptococcus mitis/oralis, which was detected in 78/181 (43.1%) of the children's isolates and 66/128 (51.6%) of the parents' isolates. Of the 311 isolates collected in this study, 282 isolates (90.7%) had an azithromycin MIC value greater than the breakpoint of 0.25 mg l^-1 and 146 isolates (46.9%) had azithromycin MICs greater than 2 mg l^-1. There was no difference in the azithromycin MIC distribution of all streptococcal isolates between children and parents. All individuals were colonized by streptococci with azithromycin MICs greater than 0.25 mg l^-1, and 87.5% of individuals had streptococci with MICs greater than 2 mg l^-1.Interpretation. The most prevalent species identified in both age groups was S. mitis/oralis. All individuals harboured streptococci with macrolide resistance. This highlights the need for additional antimicrobial stewardship initiatives to reduce the consumption of macrolides in the general population.