Presence of Virulence Genes inEnterococcusSpecies Isolated from Meat Turkeys in Germany Does Not Correlate with Chicken Embryo Lethality

Abstract

Virulence-associated traits have frequently been studied in enterococci and are considered to contribute towards the pathogenicity of infections. In the present study,Enterococcusisolates were collected during diagnostic investigations from meat turkeys in Germany. Twenty-eight isolates of three differentEnterococcusspecies were analyzed for five selected putative virulence traits to understand their potential role in the pathogenicity using the chicken embryo lethality assay. TenE. faecalis, tenE. faecium, and eightE. gallinarumisolates were examined for the presence of common virulence genes and their phenotypic expression, namely, the cytolysin operon, five individualcylgenes (cylLL,cylLS,cylM,cylB, andcylA), gelatinase (gelE), hyaluronidase (hylEfm), aggregation substance (asa1), and enterococcal surface protein (esp). TheEnterococcusisolates showed significant species-dependent differences in the presence of genotypic traits (p<0.001by Fisher’s exact test; Cramer’sV = 0.68). At least one gene and up to three virulence traits were found inE. faecalis, while sixE. faeciumisolates and oneE. gallinarumisolate did not display any virulence-associated pheno- or genotype. More than half of theEnterococcusisolates (n = 15) harbored thegelEgene, but onlyE. faecalis(n = 10) expressed the gelatinase activityin vitro. ThehylEfmgene was found in fiveE. gallinarumisolates only, while seven isolates showed the hyaluronidase activity in the phenotypic assay. In Cramer’sVstatistic, a moderate association was indicated for species (V ≤ 0.35) or genotype (V < 0.43) and the results from the embryo lethality assay, but the differences were not significant. AllE. gallinarumisolates were less virulent with mortality rates ranging between 0 and 30%. TwoE. faecalisisolates were highly virulent, harboring the wholecyl-operon as well asgelEandasa1genes. Likewise, oneE. faeciumisolate caused high embryo mortality but did not harbor any of the investigated virulence genes. For the first time,Enterococcusisolates of three different species collected from diseased turkeys were investigated for their virulence properties in comparison. The results differed markedly between theEnterococcusspecies, withE. faecalisharboring the majority of investigated genes and virulence traits. However, the genotype did not entirely correlate with the phenotype or the isolates’ virulence potential and pathogenicity for chicken embryos.