Identification and characterization of enterococci from bryndza cheese

Abstract

Aims: To identify enterococci isolated from sheep milk cheese – bryndza, and to compare differences in the composition of enterococcal microflora affected by the season, and to evaluate the potential presence of vancomycin resistance and virulence determinants. Methods and Results: Bacterial strains were isolated during analysis of bryndza cheese and identified on the genus and species level by phenotypic methods and with commercial biochemical sets. The identification of the species, Enterococcus faecium, Ent. durans and Ent. faecalis, was confirmed by PCR using species‐specific primers for ddl genes. PCR was also used for assessment of presence of vanA and vanB genes and virulence determinants gelE, agg and cytolysin genes namely: cylLL, cylLS, cylM, cylB and cylA. Among 308 Enterococcus sp. strains, 177 isolates were proved to be Ent. faecium, 59 to be Ent. durans and 41 to be Ent. faecalis. Vancomycin resistance genes vanA and vanB were not detected. Agar plate testing confirmed their absence. Gene gelE, however, was found in 20 Ent. faecalis isolates, but only 13 of them showed gelatinase‐positive phenotype. Seven isolates had five cytolysin genes, but none of the isolates exhibited a positive haemolytic phenotype. Four isolates possessed the agg gene. The prevalence of Ent. faecium species was highest in samples from the winter season harvest. Conclusions: Ent. faecium is the dominant enterococcal species in bryndza cheese and the most prevalent in the winter season product. None of the Enterococcus sp. strains was proved to have vanA or vanB genes and the vancomycin resistance. Significance and Impact of the Study: To our knowledge, this is the first report of enterococcal microflora in bryndza cheese and its evaluation for the presence of vanA and vanB genes as well as virulence determinants.

Modified 16S–23S rRNA intergenic region restriction endonuclease analysis for species identification of Enterococcus strains isolated from pigs, compared with identification using classical methods and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

“…Difficulties in obtaining definitive identification were encountered mainly in the case of E. casseliflavus, E. gallinarum, E. thailandicus and E. hirae; for instance, E. hirae was classified as E. faecalis asaccharolyticus, and E. thailandicus as E. faecium. Similar results have been obtained by other authors (Jurkovič et al, 2006;Lavová et al, 2014), which can be explained by the high homogeneity of Enterococcus spp. and the high phenotypic variability within individual species.…”

Virulence Factor and Biofilm Formation in Clinical Enterococcal Isolates of the West of Iran

“…A reason for the phenomenon could be that the presence of a specific gene does not automatically mean phenotypic expression of that gene. This could explain the presence of the gelE + isolates, which were unable to liquefy gelatine (53)(54)(55)(56).…”

Production of biogenic amines by Enterococci

“…enterococcus spp. is well known for its resistance to the heat treatment and to other physico-chemical parameters (salt content, pH), its occurrence in raw milk, fresh and semihard cheeses, pasteurised and non-pasteurised products, is common (Flint 2002;Giraffa 2003;Jurkovič et al 2006). This was proved in this study as well, in fresh cheeses (five samples) counts of enterococci were at the level 10 2 -10 6 CFU/g and in semi-hard cheeses (five samples) they were at the level 10 3 -10 5 CFU/g.…”