engleski

Characterization of enterococcal community isolated from artisan Croatian raw milk cheese ; technological and safety aspects

Introduction: Istrian cheese is artisan Croatian product that is manufactured on the Istrian peninsula from raw ewe's milk without the addition of starter cultures. Although bacteria of the genus Enterococcus is nowadays known by their beneficial effects and are considered an integral part of the natural microbiota of many traditional cheeses, some strains may present an emerging threat as human pathogens possessing antibiotic resistance and virulence traits. Therefore in depth analysis of enterococcal community to strain level is necessary in order to investigate their beneficial and safety aspects. Material and Methods: Milk, crude and Istrian cheese samples (30, 60, 90 and 120 days ripening) were collected from 6 cheese makers in 2012. Genomic DNA was extracted from isolates obtained on KAA agar. Identification of enterococci was done by PCR and sequencing the part of the 16S rRNA gene. Based on the PCR-RAPD analysis isolates were selected as representative and tested for their technological potential and potential to survive in simulated GIT conditions. Hemolysis, antibiotic resistance and the indices of genes encoding for virulence factors were determined as well. Results: Of all isolates, 47% were identified as E. faecium, 40% as E. faecalis, 2% as E. durans, 0.4% as E. gallinarum and 0.4% as E. casseliflavus. All of 35 representative isolates showed γ-hemolysis, weak to moderate proteolytic, acidifying and lipolytic activity and good survival in stimulated GIT conditions as well as pronounced antimicrobial activity. The most of the isolates were intermediately resistant or resistant to at least one of the 10 antibiotics tested and possessed multiple virulence determinants (4 to 7). Conclusion: Our data contribute new information on ecology of enterococcal community in artisan food products and may be a good base for their selection as starter or bioprotective cultures.

Istrian cheese ; Enterococcus spp ; PCR ; technological potential ; antimicrobial activity ; antibiotic resistance ; virulence genes

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