purchase Torin1 Environmental samples may contain mixed popu

Environmental samples may contain mixed populations of STEC strains, many of which could share O-type purchase Torin1 with a variety of H-antigens. It has been suggested that identifying fliC gene type may be helpful for detection of pathogenic STEC strains. Several H-types including H-, H2, H7, H8, H11, H12, H16, H19, H21, H25 and H28 are commonly associated with STEC strains. However, O serogroups when combined with different H antigens may contribute to different pathogenicity of the strains. For example, Serogroup O104 with the H7 or H21 can be more pathogenic than other combinations [32]. As a result, using commercial kits for identification of O-group to confirm the presence of pathogenic STEC may result in false positive [4]. Our results showed that there were multiple serotypes in the samples; the commercial and custom PCR screening results indicated that the samples were contaminated with two O-serotypes belonging to the Big Six group of STEC, O45 and O111. Serotype O45 combined with H2 appears to be a pathogenic strain as it harbors Shiga toxin 2 called Stx2f [33]. Our isolates, on the other hand, were identified as O45:H8, an O:H serotype combination that may not appear to be pathogenic. The microarray analysis also revealed that both isolates did not possess any of the stx and eae genes. This result also suggested that O:H serotype may reflect pathogenicity of E. coli strains. The positive result from BAX PCR for stx genes used to screen E. coli non O157:H7 STEC possibly came from the presence of O111 strains. However, due to the low population of O111 in the sample relative to O45 as shown in RT-PCR, the BAM culture method may not have enough sensitivity to allow the strain that may be responsible for the outbreak to grow. Our study strongly suggested while culture methods remain as gold standards for organism identification in foods, modern methods such as real time PCR and microarrays if used would provide concordant and additional information which could easily be escaped by culture methods due to lower limits of detection. In conclusion multidisciplinary approaches should be adopted during the outbreak investigation to help identify and characterize pathogens accurately.
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