High frequency of potentially pathogenic yeast species in goat’s raw milk and creamed cheese in Southern Brazil

There are few reports concerning isolation, counting and identification of yeasts in goat´s raw milk and derivates. The objective of this study was to evaluate the diversity of yeasts found in raw goat milk and goat creamed cheese collected in a Metropolitan area in Porto Alegre - Brazil. A simplified HMA (Heteroduplex Mobility Assay) of the 26S rDNA D1/D2 region was developed in order to rapidly confirm the identification of the isolates belonging to potentially pathogenic species. Yeasts were isolated from 59% of the samples. Fifty six strains were isolated and identified in the genera Bullera, Candida, Cryptococcus, Debaryomyces, Dekkera, Pichia, Rhodotorula, Sporodiobolus, Trichosporon, Yarrowia and Zygoascus. The average yeast count in raw milk was superior to 2 log UFC.mL-1, while cheese count was superior to 3 log UFC.g-1. Lipolytic activity was present in almost 92% of the isolates, while only 14% had proteolytic activity. Twelve potentially pathogenic ascomycetic isolates were identified by the conventional yeast identification methodology, and correspond to the species Candida parapsilosis, Candida tropicalis and Pichia guilliermondii. All of them had their identities confirmed by the simplified HMA assay. None of the isolates belonging to potentially pathogenic species were resistant to the antifungal agents tested. More studies are necessary to evaluate the real significance of the isolation of these clinically relevant yeasts