MLVA typing reveals higher genetic homogeneity among S. Enteritidis strains isolated from food, humans and chickens in Brazil in comparison to the North American Strains

Salmonella Enteritidis (S. Enteritidis) is a major causative agent of food-borne gastroenteritis associated with the consumption of contaminated poultry products. In this study we used multilocus variable number of tandem repeats (VNTRs) analysis (MLVA) to discriminate a total of 188 S. Enteritidis strains recovered from human (n = 67), food (n = 61) and chickens (n = 60) during a 24 year period (1986 through 2010) in Brazil. MLVA profiles of the 188 strains from Brazil were compared to the MLVA profiles of 100 human clinical (n = 52) and poultry-associated (n = 48) strains isolated in North America between 1986 and 2008. MLVA typing led to classification of the 288 strains from Brazil and North America into two major clusters named A and B with 35% of similarity. Cluster A consisted of a vast majority of strains isolated from North America (n = 71) and only three strains isolated from Brazil which included two pre-pandemic strains (SE5 and SE4). In contrast, cluster B consisted of all of the post-pandemic strains isolated from Brazil (n = 185) and fewer strains isolated from North America (n = 29). In general, MLVA typing showed that the North American strains were more genetically diverse whereas Brazilian strains were more genetically clonal. The clustering of pre-pandemic strains from Brazil with the North American strains suggests the possibility that the pre-pandemic strains were more likely genetically diverse; however after 1993 a new and prevalent subtype of S. Enteritidis was introduced in this country. This is the first study describing MLVA genotyping of the S. Enteritidis strains isolated from Brazil.