Virulence profiles in Enterococcus spp. isolated from raw buffalo’s milk in south Brazil

Abstract

Background and Objective: The buffalo milk consumption and derivatives have increased significantly in the last year due to the healthy food demand. Enterococci play a beneficial role during the maturation of some cheese and sausages; they have been used as probiotics in humans and animals. On the other hand, they are indicators of fecal contamination and are frequently associated with foodborne illnesses by biogenic amines. The aim of this study was to evaluate the presence of virulence profiles in enterococci strains isolated from raw buffalo’s milk samples. Materials and Methods: Seventy-nine enterococci species were selected which previously identified by conventional biochemical methods. The strains were submitted to genotypic identification using genus-specific and species-specific primers. Strains were tested for the presence of virulence genes (agg , ace , gelE ) by PCR, their ability to form biofilms and to produce the enzyme gelatinase by phenotypic methods. The optical density (OD) of bacterial biofilms was quantified in a spectrophotometer. Results: The phenotypic and genotypic identification were similar in more than 96% of the strains. The frequency of ace (96 vs. 10.34%) and gelE (96 vs. 17.24%) genes were higher in E. faecalis than in E. faecium, while the agg gene was detected only in E. faecalis strains (26%). The in vitro biofilm ability was observed in both strains; however, it was superior among E. faecalis (90%) than in E. faecium (24.1%). The presence of gelE and the activity of gelatinase were not fully concordant. Conclusion: It was concluded that the presences of enterococci harboring virulent factors in raw buffalo’s milk suggest a situation of risk for the community, since enterococci are opportunist pathogens. The ability to form biofilm is important for food safety and the protection of public health. In this sense, the present study sought to collaborate with the status quo of scientific knowledge to improve safety and quality of the food for human consumption.