Existence of Yersinia species in marketable milk and some dairy products

Abstract

Yersinia species are members of the Enterobacteriaceae . These bacteria have Gram-negative or Gram-variable, rod-shaped cells. Yersinia regards as one of the most important food-borne agents along with ability to grow at room and refrigerator temperatures. There are several intestinal and extraintestinal clinical symptoms caused by these organisms, appearing through mild gastroenteritis, mesenteric lymphadenitis, and pseudo appendicitis. Yersiniosis is a zoonotic disease with a wide distribution and a known public health significance caused by Y. enterocolitica. One hundred and sixty marketable milk samples and some milk products including kareish cheese, Domiati cheese and small-scale ice cream were collected randomly from supermarkets, dairy farms, dairy shops, and street vendors, in Assiut city, Egypt. Selective CIN (Cefsulodin-Irgasan-Novobiocin) agar plates were used after enriched by phosphate buffered saline (PBS) supplemented with novobiocin and cefsulodin and incubated at 30 °C for 24 to 48 hours. The suspected colonies were identified by biochemical tests. A total of 33 isolates (20.63%) were identified as Yersinia species , representing Y. enterocolitica (47.5%), Y. pseudotuberculosis (7.5%), Y. pestis (17.5%) and Y. intermedia (10%).