Occurrence of Escherichia coli O157 in raw material and food in Czech Republic

The study was carried out to investigate the incidence of Escherichia coli O157 in raw materials, foodstuffs and the agricultural environment. Of a total of 987 samples examined, 22 strains (2.2%) were identified as E. coli O157 and 10 of them as E. coli O157:H7. Cefixime-Tellurite MacConkey sorbitol agar (CT-SMAC) agar and Biosynth culture medium (BCM) E. coli O157:7 medium were used for the isolation. The virulence factors (stx1, stx2, eae, and ehxA genes) were identified by polymerase chain reaction (PCR). Most strains were isolated from the mechanically deboned poultry meat (nine), minced meat (six) and raw milk (four). One strain was isolated from beef carcass and two strains from waste water. No strains were were found in mass for sausages, refreshment salads, swabs of pork and poultry carcasses and faeces of cattle and pigs. Ten strains from the 22 identified proved to be positive for all factors of virulence. They were isolated from minced meat (four), raw milk (four), waste water (one) and swab from beef carcass (one). Sensitivity to the antimicrobial drugs ampicillin (AMS), ampicillin-sublactam (SAM), tetracycline (TET), ofloxacine (OFL), cefuroxime (CRX), chloramphenicol (CPM), gentamicine (GEN), colistin (COL), cephalozine (CLZ), cefoxitin (CXT), aztreonam (AZT), and sulphamethoxazole + trimethoprim (COT) was tested using the standard dilution technique and disc diffusion test. Minimum inhibitory concentrations (MIC) characteristics (MIC(50), MIC(90), MIC range) and inhibitory zone diameter were determined for each strain. As determined by MICs, the resistance to tested antibiotics in E. coli O157 isolates was found to AMS (90.9%), CLZ (81.8%), CRX (63.6%), CXT (72.7%), CPM (72.7%), TET (81.8%), SAM (59.1%), COT (9.1%), COL (63.61%), AZT (9%) and GEN (4.5%). The similar results were obtained using the disc diffusion method. The differences were found relating to SAM, CXT, CMO and TET. Resistance against one or more antibiotics was found in 95.4% of E. coli O157. Only one strain was susceptible to all tested antibiotics. Most of the strains were resistant to ampicillin and cephalozine. Eight different resistance phenotypes were demonstrated in E. coli O157.