engleski

Evaluation of virulence factors and antibiotic resistances in Enterococcus community isolated from autochthonous Istrian ewe's cheese

The diversity and dynamics of the Enterococcus community contributes to the complexity of ripening process resulting in development of organoleptic uniqueness in variety of traditional cheeses. However, their presence in food systems is matter of controversy considering that some members of genus Enterococcus are harbouring genes of antimicrobial resistance and virulence factors. The aim of the present study was to characterize the antibiotic susceptibility and to evaluate the potential presence of virulence determinants and vancomycin resistant genes (vanA and vanB) in enterococci population from autochthonous Istrian cheese. Fresh milk and cheese samples were collected from 2 dairy farms during the ripening process on monthly base. Samples were subjected to microbiological analysis. Enterococcus species were isolated on selective medium for viable count and 10-15 randomly selected colonies for each sample were Gramm stained. A total of 97 enteroccocal strains were physiologically characterized and genotyped at the genus and species level. For preliminary grouping, strains were typed using RAPD-PCR analysis with M13 and 10mer primers. According to RAPD analysis, representative strain of each RAPD group was subjected to antibiotic susceptibility testing using disc diffusion method, while the presence of the virulence factors ccf, cpd, cylM, cylA, cob, Afs, agg, gelE, cylB, Afm, esp and vanA and vanB genes was evaluated by PCR. Susceptibility to vancomycin of representative enteroccoci was also analysed with E-test method to determine the minimal inhibition concentration (MIC). The results of disc diffusion tests with six different antibiotics showed that strains were mostly resistant except two strains which were intermediately sensitive to penicillin. VanA gene was detected in one representative strain while vanB was not detected. Among representative strains all of them possessed at least one virulence determinant.

enterococci; antimicrobial suspectibility; virulence factors

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