Prevalence and Characteristics of Yersinia Enterocolitica and Yersinia Pseudotuberculosis from Raw Milk Supplied in Tehran

Foodborne diseases are caused by eating contaminated food. Yersinia species are among the bacteria involved in food contamination, such as meat, poultry, vegetables, and milk. This study aims to investigate the prevalence and characteristics of Yersinia enterocolitica and Yersinia pseudotuberculosis from raw milk in Tehran.

In this study, 360 samples of raw milk were collected from farms around Tehran and examined according to the FDA method. Then, 25 ml of milk samples were added to 225 ml of Peptone Sorbitol Bile Broth and kept for 10 days at 4 °C for enrichment. After 10 days, 0.5 ml of the sample was added to 0.5 ml of 0.72% KOH solution and 0.54% NaCl. After 30 sec, it was cultured in the selected Cefsulodin-Irgasan-Novobiocin agar (CINagar) medium to remove the normal flora. The plates were stored for 48 h at 28 °C. The suspected Bull's eye colonies were purified and phenotyping tests were carried out on the selected colony. The 20 E API kits were used for confirming identification.

From 360 raw milk samples, 4 Yersinia isolates (1.1%) including one Y. pseudotuberculosis (0.27%) and three Y. enterocolitica (0.83%) were isolated. In addition to Yersinia, other bacteria such as Klebsiella, Serratia, Citrobacter, and Providencia were isolated from milk samples.

The findings showed that clean tap water and healthy cattle in livestock can be effective in preventing Yersinia contamination. Lack of personal and environmental hygiene could cause food contamination by Yersinia and other intestinal bacteria leading to gastrointestinal infections.