Comparison of virulence factors and genetic relationships of Enterococcus faecalis strains isolated from clinical, food and poultry samples

Abstract

Enterococcus faecalis do not only inhabit the intestines of many animals, but also food and the environment. These microorganisms have intrinsic ability which enables them to persist in different environments. The aims of our study were (i) to carry out a comparative analysis of tetracycline resistance and virulence factor genes of Enterococcus faecalis isolates from food, poultry and clinical samples and (ii) to determine the genetic relationships of these factors among these isolates. A total of 182 E. faecalis were studied; 70, 52, and 60 strains were isolated from clinical samples, broiler cloacal swabs and food, respectively. Enterococcus faecalis isolates were submitted to research genes for virulence factors tet (L), tet (M), (bop ABCD, ace and agg) by PCR and grouped into clusters according to their genotype. The prevalence among all the genes studied could be considered high, ranging from 61.5 to 99.4% of the virulence factors of genes and 19.2 to 70.3% of the antimicrobial resistance genes, tet (L) and tet (M), respectively, where it was possible to obtain different genetic profiles. The enterococci isolated from food, humans and broiler cloacal swabs showed high genetic diversity, although some strains seemed to be closely related. The 182 isolates formed twelve different clusters independent of the origin of the samples or the diets used in the feeding of broilers, with the similarity index value ranging from 0.16 to 1.0, similarity coefficient, 0.70. In conclusion, enterococci isolated from food, humans and broiler cloacal swabs are genetically different. In addition, the analysis of virulence factors genes and tet genes by PCR proved to be an effective methodology for determining the microbial diversity of Enterococcus faecalis isolates of different environmental sources.