Phenotypic and Molecular Detection of Beta-Lactamase Enzyme Produced By Bacillus Cereus Isolated From Pasteurized and Raw Milk

Background: in a survey of milk samples obtained from individual farms and pasteurized milk plants in ardabil city, 38% of raw milk samples and 22% of pasteurized milk samples were found to be contaminated with bacillus cereus. in total 200 milk samples,100 of raw milk and 100 of pasteurized milk, were tested for the presence of b. cereus contamination. methods: the milk samples tested positive for b. cereus were used to isolate the dna from the and subsequently used in molecular genetic analysis. statistically, 38% of raw milk samples and 22 % of pasteurized milk samples were found contaminated with b. cereus. the results of the present study confirms that processed milk also carries a very high probability of b. cereus contamination. in the present study, three different primer sets were used to amplify dna obtained from b. cereus isolates and the gene expression profile of beta-lactamase producing genes (shv,tem,ctx-m) were analyzed using pcr. results: tem types of beta-lactamases exhibited maximum percentage frequency in raw milk isolates whereas pasteurized milk isolates had the most frequency of ctx-m type of beta-lactamases. it was observed that both raw and pasteurized milk are a source of b. cereus as evident by pure isolates obtained on agar plates. conclusion: the gene expression profile shows that milk samples are frequently contaminated with antibiotic resistant strains of b. cereus.