Abstract The aim of this study is to optimize a rapid and specific method for detection of E. coli O157:H7 (EHEC) from food samples with high background flora using an immunomagnetic separation-real-time polymerase chain reaction assay (IMS-RTiPCR). For this, EHEC cells were recovered from raw milk and ground meat samples that were artificially contaminated to the final concentrations of 101, 103 and 105 cfu EHEC/mL or g, after a non-selective pre-enrichment at 35 °C for 8 h following either with or without capturing by micro-sized beads. Then, EHEC cells were identified by RTiPCR. The study was also carried out without any enrichment to evaluate the enrichment efficiency of the assay. By comparing the assay with and without pre-enrichment, we showed that even the usage of specific micro-sized beads did not improve EHEC detection in raw milk and ground beef samples and so gave false negative results unless an 8-h pre-enrichment was applied. Besides, the assay can be completed in less than 9 h with a minimum detection limit of 103 cfu EHEC/mL or g in foods and hence was found to be simple routine-based method that exhibits great potential for implementing as a rapid screening of EHEC in microbial tests as compared to existing techniques.

In the last decade, ready-to-eat (RTE) salad vegetables are gaining increasing importance in human diet. However, since they are consumed fresh, inadequate washing during processing can bring on some foodborne illnesses, like salmonellosis, since these food items have natural contamination from soil and water. During 2009-2010, a total of 81 samples were purchased arbitrarily from local markets in Ankara, and were examined for Salmonella contamination. Salmonella screening was performed by using anti-Salmonella magnetic beads system and polymerase chain reaction (PCR) identification of the suspected colonies. Then, the antibiotic resistance profiles of four Salmonella strains identified (strains RTE-1, RTE-2, RTE-3, and RTE-4) were also investigated, since the mechanism by which Salmonella spp. have accumulated antibiotic resistance genes is of interest. All strains showed resistance against sulfonamides (MIC > 128 mg/L). Further results suggested that associated sulfonamide resistance genes were encoded by the 55.0 kb plasmid of strain RTE-1 that involves no integrons. As a result of using two primers (P1254 and P1283) in randomly amplified polymorphic DNA-PCR (RAPD-PCR) analysis, two common amplicons (364 bp and 1065 bp) were determined. The findings of this study provide support to the adoption of guidelines for the prudent use of antibiotics in order to reduce the number of pathogens present on vegetable and fruit farms. Besides, since it is shown that these bacteria started to gain resistance to antibiotics, it is necessary to further investigate the prevalence of them in foods.