Tandem Repeat Analysis for Surveillance of Human Salmonella Typhimurium Infections

Multiple-locus variable-number tandem repeats analysis improves surveillance and outbreak investigations

Variation in Antimicrobial Resistance in Sporadic and Outbreak-related Salmonella enterica Serovar Typhimurium

The prevalence of different antimicrobial resistance profiles and variants of the Salmonella genomic island 1 (SGI1) was reported for Salmonella enterica serovar Typhimurium DT104 strains isolated from patients in Denmark. Variation in antimicrobial resistance and corresponding changes of SGI1 were shown among isolates from a foodborne outbreak

Mismatch induced speciation in Salmonella: model and data

In bacteria, DNA sequence mismatches act as a barrier to recombination between distantly related organisms and can potentially promote the cohesion of species. We have performed computer simulations which show that the homology dependence of recombination can cause de novo speciation in a neutrally evolving population once a critical population size has been exceeded. Our model can explain the patterns of divergence and genetic exchange observed in the genus Salmonella, without invoking either natural selection or geographical population subdivision. If this model was validated, based on extensive sequence data, it would imply that the named subspecies of Salmonella enterica correspond to good biological species, making species boundaries objective. However, multilocus sequence typing data, analysed using several conventional tools, provide a misleading impression of relationships within S. enterica subspecies enterica and do not provide the resolution to establish whether new species are presently being formed

DNA microarray analysis of Salmonella serotype Typhimurium strains causing different symptoms of disease

<p>Abstract</p> <p>Background</p> <p><it>Salmonella enterica </it>subsp. <it>enterica </it>is one of the leading food-borne pathogens in the USA and European countries. Outcome of human <it>Salmonella </it>serotype Typhimurium infections ranges from mild self-limiting diarrhoea to severe diarrhoea that requires hospitalization. Increased knowledge of the mechanisms that are responsible for causing infection and especially the severity of infection is of high interest.</p> <p>Results</p> <p>Strains were selected from patients with mild infections (n = 9) and patients with severe infections (n = 9) and clinical data allowed us to correct for known underlying diseases. Additionally, outbreak isolates (n = 3) were selected. Strains were analyzed on a DNA-DNA microarray for presence or absence of 281 genes covering marker groups of genes related to pathogenicity, phages, antimicrobial resistance, fimbriae, mobility, serotype and metabolism. Strains showed highly similar profiles when comparing virulence associated genes, but differences between strains were detected in the prophage marker group. The <it>Salmonella </it>virulence plasmid was present in 72% of the strains, but presence or absence of the virulence plasmid did not correspond to disease symptoms. A dendrogram clustered strains into four groups. Clustering confirmed DT104 as being a clonal phagetype. Clustering of the remaining strains was mainly correlated to presence or absence of the virulence plasmid and mobile elements such as transposons. Each of the four clusters in the tree represented an almost equal amount of strains causing severe or mild symptoms of infection.</p> <p>Conclusions</p> <p>We investigated clinical significance of known virulence factors of <it>Salmonella </it>serotype Typhimurium strains causing different disease symptoms, and conclude that the few detected differences in <it>Salmonella </it>serotype Typhimurium do not affect outcome of human disease.</p