Phenotypic and Genotypic Characterization of Salmonella Isolates Recovered from Foods Linked to Human Salmonellosis Outbreaks in Minas Gerais State, Brazil

Abstract

Salmonella is one of the primary pathogens that causes foodborne diseases worldwide. In the present study, we characterized Salmonella isolates recovered from foods linked to human salmonellosis outbreaks in Minas Gerais, Brazil, from 2003 to 2017. Serotype, antimicrobial susceptibility, presence of virulence genes, and genetic polymorphism as determined by repetitive element sequence-based PCR were determined for 70 Salmonella isolates. Thirteen Salmonella serotypes were identified, and the most prevalent were Enteritidis and Typhimurium, comprising 52 (74.3%) of the 70 isolates. Sixty-five (92.8%) of the isolates were resistant to at least 1 of the 15 antimicrobials tested. Ten isolates (14.2%) had a multidrug resistance phenotype. Isolates were screened for 16 virulence genes, which were found in 75.7 to 100% of the isolates. A statistical difference was found among Salmonella serotypes in the presence of the sipB, sopE, lfpA, sefA, and spvC genes. Based on their DNA fingerprints, 40 isolates of Salmonella Enteritidis from 16 outbreaks were separated into 14 groups and 12 isolates of Salmonella Typhimurium were separated into 6 groups. These serological patterns were similar to those reported by public health centers worldwide. Of concern is the high prevalence among the isolates in this study of both virulence genes and resistance to antimicrobials, especially to critically important drugs. Special attention should be given to Salmonella Enteritidis. Although the genomes of these Salmonella isolates were relatively variable, high genetic similarity was observed among them, and some had identical fingerprints. These results support the hypothesis of clonal circulation of Salmonella isolates causing human infections in Minas Gerais.