engleski

Genetic diversity of Enterococcus species isolated from autochthonous Istrian ewe's cheese

Istrian ewe’ s cheese is traditional dairy product of Croatia. It is semi-cooked (42&ordm ; ; C), three month ripened cheese made from thermized or raw whole milk. Cheese production technology at the farmhouse level includes traditional techniques without addition of selected starter culture resulting in a significant variation in cheese quality. To standardize the technology procedure and to produce the cheese with more defined composition it is necessary to characterize the microbial community present during the cheese ripening process. The diversity and dynamics of the Enterococcus species in milk and cheese contribute to the specific characteristics of traditional cheeses and additionally is considered as a determinant factor for cheese sanitary quality and potentially pathogenic traits. The aim of the present study was to investigate diversity of Enterococcus species in Istrian cheese during the process of ripening. 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 Gramm positive isolates were further identified by combining RAPD PCR using M13 and 10 mer primers. According to RAPD-PCR grouping, genus specific primers were applied in order to characterize the isolates at genus level and species specific primers in order to identify Enterococcus species. All obtained strains were characterized as Enterococcus. The results obtained from species-specific PCR suggesting the dominance of two species, mainly E. faecalis (62%) or E. faecium (38%), such presenting the dominance of two respective species and low diversity of Enterococcus community in the investigated milk and cheese samples. MPN number of isolates was between 7.3 x 103 and 4.7 x 107 showing the lowest abundance in milk samples.

Enterococcus; RAPD PCR; strain typing

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