Investigation of Virulence Genes of Enterococcus faecalis Strains Isolated from Mastitic Bovine Milk

In this study it was aimed to investigate the potential virulence genes (gelatinase [gelE]), adhesion-associated protein [EfaAfs], enterococcal surface protein [esp], cytolysins [cylA, cylM, cylB], sex pheromones [cpd, cob, ccf], aggregation substance [aggA], enhanced expression of pheromone [eep]) of Enterococcus faecalis strains isolated from mastitic bovine milk samples with polymerase chain reaction (PCR). A total of 56 E. faecalis isolates, which were isolated from 600 bovine mastitic milk samples, were used as material. After the isolation of enterococci in selective media, identification based on genus and species were also performed using PCR. Later, the E. faecalis isolates were tested for the presence of eleven virulence factors. The efaAfs gene was the predominant (94.6%) virulence gene among the enterococci investigated followed by cpd (91.0%), gelE (87.5%), esp (51.7%), ccf (42.8%), cob (10.7%), eep (8.9%), aggA (7.1%), cylA and cylM (1.8%). cylB gene were not detected in any of isolates. 1.8% and 3.6% of the strains harboured eight and seven virulence determinants, while there was no isolate having no virulence genes. Studies on the prevalence of enterococci in dairy cattle have been reported however there is still a lack of information regarding virulence genes of enterococci isolated from mastitic bovine milk. To the best knowledge of the authors this is the first report describing virulence genes of E. faecalis isolated from bovine mastitic milk in Turkey. It was concluded that E. faecalis strains isolated from mastitic bovine milk were found to be highly pathogenic with potential risk factors for consumer health. Further epidemiological studies are necessary to investigate the status of virulence factors of other enterococci isolated from mastitic bovine milk in the veterinary field.