Posted: July 28th, 2010 - 7:32am
Source: Journal of Food Safety

ABSTRACT
Detection limits and the survival of Yersinia enterocolitica in goat cheese were determined by culture and by nested polymerase chain reaction (PCR). Thirty goat cheese samples inoculated with 104 to 101 cfu/g Y. enterocolitica O:9 or O:3 strains were enriched for 0, 3 and 18h in trypticase soy broth (TSB), modified Rappaport broth and a formulated in our laboratory broth (FLB). The lowest detection limits were 1 × 103 cfu/g by culture on Mac Conkey agar after 3 h TSB and FLB enrichments, and 1 × 102 cfu/g by nested PCR at 3 h from all enrichment broths. Y. enterocolitica survival was studied in 20 goat cheese samples contaminated at levels of 1 × 106 cfu/g and stored at 4° and 22C for 120 days. Y. enterocolitica was detected during 7 and 30 days at 22C and 4C, respectively. Total and fecal coliforms were recovered from microflora of goat cheese, but indigenous Y. enterocolitica was not detected.
PRACTICAL APPLICATIONS
In San Luis, Argentina, Yersinia enterocolitica strains have been isolated from several foods, samples of animal origin and stool specimens from symptomatic patients. This is the first survey of this microorganism in goat cheese manufactured in our region. The performance of two detection methods, culture and nested polymerase chain reaction, was evaluated in the assessment of the detection limits and the survival of this pathogen in goat cheese. Results might contribute to the knowledge of the behavior of Y. enterocolitica in this food and reinforce the increasing concern about the microbiological quality of this dairy product. Survival of Y. enterocolitica in goat cheese represents a hazard for the consumer health.