جداسازي ليستريامونوسيتوژن از پنير با استفاده از روش غني سازي در سرما و مشاهده باكتري در كشت سلولي هلا

Isolation of Listeria Monocytogenes from Cheese by Cold Enrichment Method and Detection of this Bacteria in Hela Cell Culture

Background: Listeria monocytogenes is frequently transmitted from contaminated food such as cheese, raw vegetables, prepacked salad and etc, to humans. This bacteria can grow inter and extracellular. The aim of this study was to present a simple practical method for isolation of this bacteria from cheese, and detection of it in Hela cell culture by light microscopy Materials and Methods: In this experimental study, the sample of fresh local cheese was suspended in selective enrichment medium with yeast extract and kept at 4°C for one week. Then, the sample was diluted with potassium hydroxide and cultured on Palkam and Listeria Selective agar. After colonies appeared, they were examined for the existance of L. monocytogenes and then were inoculated in Hela cell culture. Samples were taken intervally (12, 24, 36, 48 hrs), stained with Gimsa, detected by light microscopy and photographed. Results: This study showed that 9% of fresh local cheese was contaminated by L. monocytogenes. Pictures, taken by microscope, indicated that this bacteria in concentration more than 5x 10^5 after 12 hours can enter into Della cells and after 48 hours lysed the host cells. Conclusion:The results of this study showed that L. monocytogenes exist in some contaminated local cheese. Contamination of dairy products by Listeria monocytogenes can occur during preparation, transport and distribution. So, because of the high consumption of these products in our country, it is necessary to specific surveillance of the production and distribution of dairy products to prevent the incidence of listeriosis in susceptible people.