[Isolation of shigatoxin-producing Escherichia coli [STEC] from meat samples by PCR in Tehran and evaluation of antibacterial patterns of isolated strains]

ABSTRACT

Shigatoxin-producing Escherichia coli [STEC] is an emerging foodborne pathogen of worldwide public health importance. This bacterium has been reported as an etiological agent of many outbreaks and sporadic cases. Studies in different countries have shown that food items maybe contaminated by this pathogen. The present study was carried out to determine the frequency of STEC contamination of meat samples, collected in Tehran, as well as defining genotype and antibiotic susceptibility patterns of isolated bacteria. In a period of one year [from 1 July 2004 to 30 June 200, 250 beef samples were collected from different markets of Tehran city. For detection and isolation of STEC from beef samples, conventional culture and PCR were applied. Then, Antibacterial resistance patterns of isolated strains were determined by standard disk diffusing method. Among 250 beef samples, 47[18.8%] were positive for stx genes by PCR. However, only 30[12%] successful isolations of bacteria were made. Of the 30 STEC isolates, 24 [80%] carried the stx2 gene only, while 2 [6.7%] isolates gave positive results for both stx1and stx2. Four isolates [13.3%] possessed stx2 and eae genes. According to the antibiotic resistance tests, all isolates were susceptible to Gentamicin, Imipenem, Norfluxacin, Enrofloxacin, Nalidixic acid, Ciprofluxacin and Ceftazidime. The percentages of isolates that were resistance to the other antibacterial agents were as following Olendeomycin100, Erythromycin100, Cephalothin67, Amoxycillin-Clavulanic acid 46.6, Chlortetracycline 13.3, Tetracycline 10 and Streptomycin 6.6. Results of this study indicate that retail raw meats may often be contaminated with antimicrobial-resistant STEC and cautionary efforts are necessary in order to prevent them from contaminating with this bacterium