Caracterização fenotípica e molecular de marcadores de virulência em cepas de Escherichia coli isoladas de alimentos de origens diversas

Abstract

Food is implicated in the spread of Escherichia coli strains with pathogenic potential. This study aimed to investigate the virulence profile in 339 strains of E. coli, recovered from food, namely: parsley (Petroselinum crispum); frozen chicken carcasses; seafood: mussels, clams, and oysters; pasteurized milk and mashed potatoes from the diet for patients admitted to a teaching hospital. Using PCR, phylogenetic groups and virulence genes were investigated, such as: eae, bfpA, bfpB, stx1, stx2, ltA, est, ipaH, aggR, aatA, associated with diarrheagenic E. coli (DEC) and the markers fimH, papEF, pap GII and III, sfa, afa, hlyA, cfn1, tratT, aer, flu and PAI, associated with extra-intestinal pathogenic E. coli (ExPEC), specifically uropathogenic E.coli. In addition, serogroups O157; O26; O45; O103; O111: O121; O145 and the H7 flagellar antigen in the O157 strains were investigated. Strains exhibing molecular virulence profile were submitted to phenotypic adherence assays with HEp-2 cells and strains harboring the stx2 gene to the Vero cell cytotoxicity assay. Phylogenetic group A was observed in all food sources, and it was also the most prevalent among strains in this study (48%), followed by groups B1 (32%), D (12%) and B2 (8%). Virulence markers were found in 32.7% of the strains and 29 distinct virulence profiles were observed. Highlighting the stx2 that was the most frequent gene, alone or together other markers, observed in 45 strains, characterizing them as STEC. None strains were associated with ETEC, EIEC and EAEC and a single one exhibed molecular profile compatible with typical EPEC (tEPEC), however localized adherence phenotype was not observed. 54% and 27% of the total, exhibed molecular markers associated to ExPEC and DEC, respectively. Curiously, 19% carried genes related to both categories. Among different food source, mashed potatoes showed the highest frequency of virulence markers (89%), most of all were classified as STEC. Serogroups O121, O103 and O145 were found in parsley, chicken and mussel, respectively. Serogroup O157 was observed only in E. coli recovered from mashed potatoes, nevertheless H7 flagellar antigen was not present. Using cytotoxicity assay, none strain expressed the Shiga toxin production phenotype. In conclusion, foods from different sources, including ready-to-eat food for hospitalized patients, carried E. coli strains harboring molecular and phenotypic markers of virulence, and may play an important role in the dissemination of these genes. The results highlighted the importance of conducting/reviewing the procedures of good food production practices, in order to minimize the transmission of these microorganisms and the occurrence of foodborne diseases.