Salad is one of the most popular components of the diets. E. coli Shiga toxin producing STEC is considered as one of the most important food pathogens. This study aimed to investigate the prevalence of salad contamination with this pathogen in Isfahan city and Chaharmahal va Bakhtiari Province STEC, determine the pattern of antibiotic-resistant and tracking virulence genes in bacteria were isolated. In this study, eighty samples of salad were randomly collected from Chaharmahal va Bakhtiari Province and Isfahan city from fast food restaurants and shopping malls. Following isolation of E. coli in the culture, PCR test to determine the virulence factors, Shiga toxin-producing bacteria was performed using specific primers. Then antibiotic resistance patterns were determined by standard methods and disk diffusion. The results showed that 80 salads, 11 samples (13/75 percent) are infected with E. coli. All strains of E. coli are resistant to at least one antibiotic. The highest and the lowest resistance were observed in tetracycline (58.82 percent) and nitrofurantoin (3.92%), respectively. The lowest prevalence and Stx1 had the highest frequency in the virulence genes. However STEC strains are not highly virulent in Iran, the findings of this study showed the possibility of contamination of the salads offered at fast food centers and restaurants. Therefore, preventive measures to avoid salad contamination with these bacteria are necessary.
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