Clonal Relatedness of Enterotoxigenic and Enteropathogenic Escherichia coli Isolates from Diverse Human, Foods and Calf Sources

Background: Foodborne infection caused by EnterotoxigenicEscherichia coli (ETEC) and Enteropathogenic Escherichia coli (EPEC) is one of the major health problems, particularly in the developing countries. Therefore, it is vital to identify the origin of food contamination to plan control strategies efficiently. Method: A total of 219 E. coli isolates from human and calf feces, raw meat, and dairy product samples were screened for virulence genes of ETEC and EPEC pathotypes by duplex-PCR assay. Then, rep-PCR was performed for the pathotypes. DNA fingerprints were analyzed with NTSYS-pc program, and dendrogram was generated. Results: Among the E. coli isolates, ETEC (6.4%), typical-EPEC (3.2%) and atypical-EPEC (5.5%) were detected. Dendrogram analysis showed two clusters; all human ETEC isolates and one meat ETEC isolate were grouped under cluster A, and all EPEC isolates collected from the four sources along with two animal fecal ETEC isolates and one ETEC isolate from meat products were grouped under cluster B. According to Jackknife analysis, the average percentage of ETEC and EPEC strains that were accurately clustered were 98% and 93.75%, respectively. Conclusion: Animal source food (ASF) isolates were placed in the same phylogenetic group as calf isolates. Moreover, the positioning of human and animal isolates in two separate groups suggested the genetic diversity between these two groups. Thus, it could be argued that E. coli isolates from animals may be transmitted via meat and dairy products, emphasizing the necessity of applying more accurate standards in the processing of ASFs.