survival of escherichia coli o157:h7 and listeria monocytogenes in doogh, a traditional iranian dairy beverage

background: unlike industrially production, iranian traditional doogh are not pasteurized after production. hence, possible contamination with different pathogenic bacteria may occur during production or post-production of traditional doogh. the aim of the present study was to monitor the behavior of escherichia coli o157:h7 and listeria monocytogenes in traditional iranian doogh at different temperatures and time periods. methods: low acid and high acid doogh samples were inoculated with approximately 4 and 6 log cfu/ml of each pathogen separately and incubated at 4 ºc and 25 ºc. at different time interval, samples were taken to enumerate e. coli o157:h7 and l. monocytogenes and determine titratable acidity. results were analyzed by anova test using spss software (v. 16.0). results: although the survival ability of e. coli o157:h7 in doogh samples was slightly higher than l. monocytogenes, both of them were detected in low acid doogh sample after 10-14 days at 4 ºc. however, they were not detected in low acid doogh samples for more than 2 days at 25 ºc. in contrast, in high acid doogh samples, the viability of e. coli o157:h7 and l. monocytogenes declined more quickly to undetectable level, both at 4 ºc and 25 ºc indicating less viability of these bacteria in high acid doogh samples compared to those of low acid ones (p<0.05). conclusion: traditional iranian doogh should be considered as a potential vehicle of transmission of e. coli o157:h7 and l. monocytogenes, especially in low acid doogh samples when stored under refrigeration.