Detection and survival of Yersinia enterocolitica in goat cheese produced in San Luis, Argentina

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 1×103cfu/g by culture on Mac Conkey agar after 3h TSB and FLB enrichments, and 1×102cfu/g by nested PCR at 3h from all enrichment broths. Y. enterocolitica survival was studied in 20 goat cheese samples contaminated at levels of 1×106cfu/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.