Project description:A collection of 61 Salmonella enterica serovar Typhimurium (S. Typhimurium) of animal and human origin, matched as closely as possible by phage type, antimicrobial resistance pattern and place / time of isolation, and sourced from farms or hospitals in Scotland, were analysed by antimicrobial susceptibility testing, phage typing, pulsed field gel electrophoresis (PFGE), plasmid profiling and DNA microarrays. PFGE of all 61 isolates revealed ten PFGE profiles, which clustered by phage type and antibiotic resistance pattern, with human and animal isolates distributed between PFGE profiles. Analysis of 23 representative S. Typhimurium strains hybridised to a composite Salmonella DNA microarray identified a small number of specific regions of genome variation between different phage types and PFGE profiles. These variable regions of DNA were typically located within prophage-like elements. Simple PCR assays were subsequently designed to discriminate between different isolates from the same geographical region.
Project description:Salmonella enterica serovar Typhimurium (S. Typhimurium) definitive phage type 104 (DT104) has caused significant morbidity and mortality in humans and animals for almost three decades. We have completed the full DNA sequence of one DT104 strain, NCTC13348 and show that the main differences between the genome of this isolate and the previously sequenced S. Typhimurium LT2 lie in integrated prophage elements and the Salmonella Genomic Island 1 encoding antibiotic resistance genes. Thirteen isolates of S. Typhimurium DT104 with different pulsed field gel electrophoresis (PFGE) profiles were analyzed by multi locus sequence typing (MLST), plasmid profiling, hybridization to a Pan-Salmonella DNA microarray and prophage-based multiplex PCR. All the isolates belonged to a single MLST type ST19. Microarray data demonstrated that the 13 DT104 isolates were remarkably conserved in gene content. The PFGE band-size differences in these isolates could be explained to a great extent by changes in prophage and plasmid content. Thus, here the nature of variation in different S. Typhimurium DT104 isolates is further defined at the genome level illustrating how this phage type is evolving over time.
Project description:Candida tropicalis is a leading cause of invasive candidiasis in the Asia-Pacific region, with mortality rates exceeding 50%. The rising prevalence of azole resistant clinical strains, particularly in this region, presents a significant clinical challenge. In this study, we analyzed 1,032 C. tropicalis isolates, including 1,016 clinical isolates collected over nine years from 27 hospitals across India, as well as 16 environmental isolates. Fluconazole resistance was detected in 5.1% of clinical isolates, with more than half also exhibiting cross-resistance to voriconazole and itraconazole. Multilocus sequence typing (MLST) and phylogenomic analysis of 1,571 global isolates, confirmed the clonal emergence and persistence of azole- resistant MLST clade 4 strains in Indian hospitals. Genomic analysis revealed that Indian isolates cluster closely with azole resistant strains from China, Singapore, and Taiwan. Azole resistance was found to be multifactorial, involving well-characterized hotspot mutations in the ERG11 gene (Y132F, S154F), ERG11 gene amplification (2–7.5 copies), and significant overexpression of ERG11. Transcriptomic profiling showed significant up regulation of virulence-associated genes in the fluconazole-resistant isolate. Notably, ALS7, a member of the agglutinin-like sequence (ALS) family involved in cell adhesion along with Secreted Aspartyl Proteinases (SAP) genes SAP7 and SAP9, were significantly upregulated in fluconazole-resistant isolates. Additionally, fluconazole-resistant isolates exhibited significantly enhanced biofilm formation compared to fluconazole-susceptible strains, indicating a higher virulence potential. Furthermore, fluconazole-resistant isolates exhibited reduced β-glucan exposure, a trait linked to immune evasion, and showed greater survival in both neutrophil and macrophage killing assays. Together, our findings provide comprehensive genomic and phenotypic evidence supporting the emergence, persistence, and increased pathogenic potential of azole-resistant C. tropicalis clade 4 in Indian hospitals. A deeper understanding of the epidemiological trends and molecular mechanisms driving drug resistance in C. tropicalis is essential for improving diagnostic accuracy, optimising antifungal susceptibility testing, and informing effective clinical management strategies.
