en تخصصي Special Original article Original article <p style="text-align: justify"><span style="font-family:times new roman"><strong>Background:</strong> 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 <em>Escherichia coli</em> O157:H7 and <em>Listeria monocytogenes </em>in traditional Iranian doogh at different temperatures and time periods.</span></p> <p style="text-align: justify"><span style="font-family:times new roman"><strong>Methods:</strong> 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 ^&ordm;C and 25 ^&ordm;C. At different time interval, samples were taken to enumerate <em>E. coli</em> O157:H7 and <em>L. monocytogenes</em> and determine titratable acidity. Results were analyzed by ANOVA test using SPSS software (v. 16.0).</span></p> <p style="text-align: justify"><span style="font-family:times new roman"><strong>Results:</strong> Although the survival ability of <em>E. coli</em> O157:H7 in doogh samples was slightly higher than <em>L. monocytogenes</em>, both of them were detected in low acid doogh sample after 10-14 days at 4 ^&ordm;C. However, they were not detected in low acid doogh samples for more than 2 days at 25 ^&ordm;C. In contrast, in high acid doogh samples, the viability of <em>E. coli</em> O157:H7 and <em>L. monocytogenes</em> declined more quickly to undetectable level, both at 4 ^&ordm;C and 25 ^&ordm;C indicating less viability of these bacteria in high acid doogh samples compared to those of low acid ones (<em>p</em><0.05).</span></p> <p style="text-align: justify"><span style="font-family:times new roman"><strong>Conclusion:</strong> Traditional Iranian doogh should be considered as a potential vehicle of transmission of <em>E. coli</em> O157:H7 and <em>L. monocytogenes</em>, especially in low acid doogh samples when stored under refrigeration.</span></p> Escherichia coli O157, Listeria monocytogenes, Dairy Products, Survival 122 127 http://jfqhc.ssu.ac.ir/browse.php?a_code=A-10-1-116&slc_lang=en&sid=1 M. Zarei zarei@scu.ac.ir Yes Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran A. Fazlara No Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran M. Pourmahdi Borujeni No Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran M. Karimi No Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran