Prevalence and antimicrobial resistance of Escherichia coli O157 isolated from traditional cheese, ice cream and yoghurt in Iran

Abstract

Verotoxin-producing of Escherichia coli O157 is an increasingly common cause of severe gastrointestinal illness, enlisted among the most important emerging pathogens. The present study was conducted to investigate the presence of E. coli O157 and E. coliO157: H7 strains and to detect the presence of the stx1, stx2, eae and ehxA insolates derived from 290 samples (120 samples from traditional fresh cheese, 120 samples from traditional ice cream and 50 samples from yoghurt). The samples were purchased from the Isfahan, Chaharmahal, Bakhtyari and Khuzestan provinces in Iran, over a period 6-month from August 2010 to February 2011. Standard cultural method and polymerase chain reaction were applied for these analyses. E. coli O157 was detected in nine of the 290 (3.1%) samples tested (five isolated from traditional cheese and 4 isolated from traditional ice cream samples), whereas E. coli O157: H7 was not detected in any samples. The genes stx1 and stx2 were detected in three E. coli isolated obtained from traditional cheese samples none of the stx1, stx2, eae and ehxA was detected in the E. coli isolates obtained from traditional ice cream samples. Susceptibilities of nine E. coliO157 isolates were determined for ten antimicrobial drugs using the disk diffusion assay. Resistance to ampicillin and gentamycin was the most common finding (44.4%), followed by resistance to erythromycin (33.3%), amoxicillin (11.1%), tetracycline (11.1%) and nalidixic acid (11.1%). All E. coli O157 isolates were susceptible to chloramphenicol, cefuroxime, and streptomycin. Thus, traditional cheese and ice cream manufactured from unpasteurized milk have appositional risk as a result of E. coli O157 existence. Key words: Escherichia coli O157, cheese, ice cream, yoghurt.