Project description:We have performed microarray hybridization studies on forty clinical isolates from twelve common serovars within Salmonella enterica subspecies I (sspI) to identify the conserved gene pool present.
2005-12-06 | E-SGRP-1 | biostudies-arrayexpress
Project description:MCR-1 positive Salmonella Clinical isolate in China
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:Salmonella enterica variants exhibit diverse host adaptation, outcome of infection, and associated risk to humans. Analysis of 6,335 Salmonella isolates recovered from integrated human-animal surveillance in Emilia Romagna region, Northern Italy, (human population ca 4,500,000), from 2012 to 2017 showed that Salmonella enterica serovar Derby constitutes a swine associated serovar in this epidemiological context while representing also a significant causative agent of human infections. Comparison of the distribution of subtypes of Salmonella Derby from human and swine identified isolates with a distinct PFGE profile that were significantly less isolated in human infections than in swine infections compared to all other subtypes. Here we show that isolates with this PFGE profile form a distinct phylogenetic sub-clade within Salmonella Derby and exhibit a marked reduction in invasion and replication in human epithelial cells but a relatively small reduction in swine epithelial cells, in line with the epidemiological evidence. A single missense mutation in hilD, that encodes the master-regulator of the Salmonella Pathogenicity Island 1 (SPI-1), was identified in this lineage of Salmonella Derby. Since SPI-1 encodes for a primary system of Salmonella invasion into epithelial cells, we investigated the role of the observed mutation in detail. We demonstrated that the missense mutation results in a loss of function of HilD that accounts for the reduced invasion and replication in human epithelial cells while showing a relatively small impact on the interaction with swine cells. This finding is suggestive of a mechanism of invasion alternative to SPI-1 in the Salmonella-swine combination
Project description:WGS of mcr-4 positive Salmonella enterica serovar Typhimurium in clinical isolates of human origin, Italy, October to November 2016
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:Comparative genomic analysis of the most important S. enterica sspI clinical isolates and respective strains from the SARB collection Keywords: other
Project description:Salmonella Heidelberg is currently the 9th common serovar and has more than twice the average incidence of blood infections in Salmonella. A recent Salmonella Heidelberg outbreak in chicken infected 634 people during 2013-2014, with a hospitalization rate of 38% and an invasive illness rate of 15%. While the company’s history suggested longstanding sanitation issues, the strains’ characteristics which may have contributed to the outbreak are unknown. We hypothesized that the outbreak strains of S. Heidelberg might possess enhanced stress tolerance or virulence capabilities. Consequently, we obtained nine food isolates collected during the outbreak investigation and several reference isolates and tested their tolerance to processing stresses, their ability to form biofilms, and their invasiveness in vitro. We further performed RNA-sequencing on three isolates with varying heat tolerance to determine the mechanism behind our isolates’ enhanced heat tolerance. Ultimately, we determined that (i) many Salmonella Heidelberg isolates associated with a foodborne outbreak have enhanced heat resistance (ii) Salmonella Heidelberg outbreak isolates have enhanced biofilm-forming ability under stressful conditions, compared to the reference strain (iii) exposure to heat stress may also increase Salmonella Heidelberg isolates’ antibiotic resistance and virulence capabilities and (iv) Salmonella Heidelberg outbreak-associated isolates are primed to better survive stress and cause illness. This data helps explain the severity and scope of the outbreak these isolates are associated with and can be used to inform regulatory decisions on Salmonella in poultry and to develop assays to screen isolates for stress tolerance and likelihood of causing severe illness.
