Comparison of microbial culture and PCR methods to detect E. coli in milk

Escherichia coli is the most common aerobic organisms in human gut and some other warm-blood animals. It is Indicator of fecal contamination of food and water. According to available reports E.coli can be transmitted to humans through the water, meat, milk and its products. Considering that the milk is a valuable food in the food basket families, bacteriological quality control of raw and pasteurized milk is critical in production facilities, milk collection and processing. Successive cultivation methods for detection of E.coli was also very time consuming and have low accuracy and may cause false positive results. Polymerase Chain Reaction (PCR) is sensitive, accurate, inexpensive and fast method that can substitute for common testing methods. In this study grown on medium trips through standard and PCR molecular techniques were compared. For this purpose, 50 samples of raw and pasteurized milk were collected. DNA were done extracted by boiling method then evaluated by optimized PCR and Results of PCR reactions were evaluated on agarose gel. For cultivation 9 tubes MPN used at first then the tube containing the gas cultured on the EMB medium by linear method. Among the 50 samples of raw milk, PCR test result evaluated positive in 24 samples but the microbial culture was positive in 20 samples and among the 50 samples of pasteurized milk, PCR test result evaluated positive in 29 samples but microbial culture results in no instance was positive. This study showed that the PCR method compared with the successive cultures methods is more sensitive, and able to detect E.coli in milk with high specificity and less time.