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Salmonella entericaserovar Enteritidis is frequently isolated from animal-source foods associated with human salmonellosis outbreaks. This serovar was spread to animal (mainly poultry) farms worldwide in the 1980s, and it is still detected in foods produced in many countries, including Brazil. The present study reports a retrospective genome-wide comparison of S.Enteritidis from foodborne outbreaks in Southern Brazil in the last two decades. Fifty-two S.Enteritidis isolates were obtained from foodborne outbreaks occurring in different cities of the Brazilian southernmost State, Rio Grande do Sul (RS), from 2003 to 2015. Whole-genome sequences (WGS) from these isolates were obtained and comparatively analyzed with 65 additional genomes from NCBI. Phylogenetic and Bayesian analyses were performed to study temporal evolution. Genes related to antibiotic resistance and virulence were also evaluated. The results demonstrated that all S.Enteritidis isolates from Southern Brazil clustered in the global epidemic clade disseminated worldwide originally in the 1980s. Temporal analysis demonstrated that all Brazilian isolates had a tMRCA (time to most recent common ancestor) in 1986 with an effective population size (Ne) increase soon after until 1992, then becoming constant up to now. In Southern Brazil, there was a significant decrease in the spreading of S. Enteritidis in the last decade. In addition, three antibiotic resistance genes were detected in all isolates: aac(6′)-Iaa, mdfA, and tet(34). These results demonstrate the high frequency of one only specific S.Enteritidis lineage (global epidemic clade) in foodborne outbreaks from Southern Brazil in the last two decades.

Salmonellastrains (n= 75) isolated from foods involved in foodborne outbreaks occurred in Rio Grande do Sul State, Brazil, during 1999 and 2000 were studied. Strains were serotyped and submitted to PCR analysis to verify the prevalence of Salmonellaplasmid virulence (spvR) regulatory gene. Among the 75 isolates, 73 (97%) were classified as Salmonella entericaserovar Enteritidis. All of the Salmonellastrains isolated in 1999 were classified as serotype Enteritidis, whereas in 2000 two isolates were serotyped as SalmonellaDerby and SalmonellaTyphimurium. Regarding the prevalence of spvRgene, 62 strains (82.7%) were PCR positive, and a positive correlation (P< 0.05) between the strains of SalmonellaEnteritidis and the presence of spvRgene was demonstrated, which suggests that this gene is a characteristicof the SalmonellaEnteritidis analyzed.