Ascertaining the relationship between Salmonella Typhimurium and Salmonella 4,[5],12:i:- by MLVA and inferring the sources of human salmonellosis due to the two serovars in Italy

Abstract

The current picture of human salmonellosis shows Salmonella Typhimurium and S. 4,[5],12:i:- as the most common serovars in Italy. The aims of this study were to investigate the genetic relationship between these serovars, as well as to test the possibility of inferring sources of human salmonellosis due to S. Typhimurium and S. 4,[5],12:i:- by using multilocus variable-number tandem repeat analysis (MLVA) subtyping data. Single isolates from 268 human sporadic cases and 325 veterinary isolates (from pig, cattle, chicken, and turkey) collected over the period 2009–2011 were typed by MLVA, and the similarities of MLVA profiles were investigated using different analytical approaches. Results showed that isolates of S. 4,[5],12:i:- were more clonal compared to S. Typhimurium and that clones of both serovars from different non-human sources were very close to those which were responsible for human infections, suggesting that source attribution by MLVA typing should be possible. However, using the Asymmetric Island Model it was not possible to obtain a confident ranking of sources responsible for human infections based on MLVA profiles. The source assignments provided by the model could have been jeopardized by the high heterogeneity found within each source and the negligible divergence between sources as well as by the limited source data available, especially for some species.

Contributions of P2- and P22-like prophages to understanding the enormous diversity and abundance of tailed bacteriophages

“…Among the latter four, we examined prophage panels from Typhimurium and Newport and found them to carry at least 10 and 5 different types of P22-like prophages, respectively (Figures S13 and S14). Newport, Agona and Bareilly are all polyphyletic serovars (Sangal et al , 2010; Achtman et al , 2012; Cao et al , 2013; Timme et al , 2013; Zhou et al , 2013) and Typhimurium is substantially more diverse than Typhi (Lan et al , 2009; Bell et al , 2011; Barco et al , 2015). Thus, there is a noticeable but imperfect correlation between uniformity of P22-like prophage contents and overall serovar genetic uniformity.…”

Pathogenicity and Competitive Fitness of Salmonella enterica Serovar 4,[5],12:i:- Compared to Salmonella Typhimurium and Salmonella Derby in Swine

“…Although S. 4, [5],12:i:has been reported more frequently, additional research is needed to evaluate the specifics of its pathogenicity in swine. Based on published research using multiple-locus variable number tandem repeat analysis (MLVA), phage typing, pulsed-field gel electrophoresis (PFGE), polymerase chain reaction (PCR), and whole-genome sequencing (WGS), it is highly likely that S. 4, [5],12:i:-is a monophasic variant of S. Typhimurium (9)(10)(11)(12)(13)(14)(15)(16). Thus, S. 4, [5],12:i:-could resemble the disease-causing ability of S. Typhimurium.…”

Phenotypic and Genotypic Eligible Methods for Salmonella Typhimurium Source Tracking

“…The Dutch model does not account for differences in the ability of subtypes and sources to infect humans (Mughini-Gras and van Pelt, 2014 ). It always provides attributions in a rather proportional and straight way and makes the arguable assumption of an equal impact of the different subtypes and sources to the human population (Barco et al, 2013 , 2015 ; Mughini-Gras et al, 2014b ). The Danish model compares the number of human cases caused by different Salmonella subtypes with their prevalence in different food sources, but this model also incorporated bacterial and food source dependent factors.…”