Backgrounds: O157:H7 E. coli has been implicated in the worldwide outbreak of food and water borne diseases. Early and effective diagnosis are the pivotal concerns for clinics and hospitals for prompt reporting of outbreaks, prevent more cases and treat the infection in appropriate time. Most of common diagnostic methods are constrained by significant drawbacks and novel reliable and rapid detection of this pathogen is beneficial to execute, particularly in low-resource laboratory settings. This study aimed at evaluating the performance of LAMP diagnostic assay targeting on putative fimbria protein coding gene (Z3276) for rapid and specific detection of EHEC O157:H7. Results: A total number of 40 locally available bacteria isolates and reference strains, among them 6 entrohemorrhagic (O157:H7) and 10 entropathogenic E. coli, 7 non diarrheic E. coli strains and 13 non entrohemorrhagic shiga toxic (stx) E. coli isolates as well as 4 pathogenic non E. coli species were included to optimization and evaluation for LAMP assay. The LAMP amplified DNA samples were visualized as turbid DNA with naked eye as well as using gel electrophoresis followed by staining. The assay performed with 100% (6/6) sensitivity, 97.05% (33/34) specificity, as well as 97.5% (39/40) efficiency. The assay was exhibited with 100% negative predicted value and 85.7% positive predicted value. The LAMP assay was also 10 times more sensitive than the conventional PCR assay; sensitivity evaluation was done through serial dilution. Additionally, LAMP and PCR assay results showed very high agreement (k = 0.97) on detection of the studied bacteria. Conclusions: Different diagnosis methods have been developed for EHEC O157:H7 detection. Nevertheless, some of the developed assays are not effective and others are expensive. In this study simple, rapid, specific and sensitive molecular diagnostic assay (LAMP assay) for detection of EHEC O157: H7 were evaluated. Thus, in comparison with performance of PCR and SMAC, LAMP assay was loftier in sensitivity, rapidness and cost-efficiency. Through further improvement, LAMP assay can be exploiting as point care diagnostic assays in resource-limited laboratories, especially in rural clinics and primary hospitals.

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Shiga toxin-producing Escherichia coli (STEC) are the leading pathogenic strain causes of diarrhea diseases and death of humans in worldwide. Many diagnostic assays have been developed to aid for the diagnosis of STEC strain; however, they have different limitations. Thus, this study was aimed at designing rapid, effective, sensitive and specific immunodiagnostic assay for STEC strain detection. Thus, a STEC isolate available was recovered from freezer in EMB agar; then a pure typical growth was inoculated into TSB overnight at 37oC. The broth culture was processed using chloroform methanol extraction method for purification of LPS from the bacteria. Assessment on SDS-PAGE showed that the LPS preparation was contaminated by small amount and identity of cellular proteins. The produced antibody showed positive agglutination both on the purified LPS as well as the STEC isolate carrying LPS on their surface; however, agglutination of STEC was more pronounced. Mice immunized with LPS produced highest agglutination on tertiary immunization showing the progressive buildup of the antibody response against the antigen. Cultures from TSA and when they refresh showed better agglutination than cultures on EMB as well as TSB. Immunodiagnostic assay developed in this study could detect STEC strains including STEC in human feces with rapidly (1–2 minutes), sensitively (90.2%), specifically (89.5%) and accurately (90.6%). However, further studies are still required to improve it sensitivity, specificity and reproducibility. Overall this diagnostic assay provided promising results that may curb current problem with detection methods in clinical health care and research laboratories.