Evaluation of cultural, immunological and molecular methods in identifying Escherichia coli O157:H7 strain isolated from clinical and environmental sources

Aims:The current study evaluates the efficiency of different identification methods of Escherichia coli O157:H7 strain isolated from clinical and environmental sources.Methodology and results: Three culture media were used, Sorbitol MacConkey agar (SMAC) medium, CHROM agar medium and E. coli O157:H7 medium.The immunological identification was performed by ELISA technique, while molecular identification was performed by PCR targeting the 16SrRNA gene.In primary isolation, 90 E. coli isolates were obtained from clinical sources, of which 43(47.8%) were identified as E. coli O157:H7 strain by culture method.In comparison, 51 isolates were obtained from environmental sources and 29(56.8%)were identified as the E. coli O157:H7 strain.The CHROM agar was the best cultural medium compared to other media in the case of clinical and environmental samples, by sensitivity rate reached 80% and 90%, respectively.In addition, the immunological method confirmed the diagnosis of 28 samples (82.3%) of the total isolates diagnosed by culture, while the molecular method confirmed the diagnosis of 25 samples (73.5%).Conclusion, significance and impact of study: It is concluded that there is a variation in the specificity and sensitivity of different methods used to identify E. coli O157:H7 strain.