Frequency of k99, stx1, and stx2 Virulence Factors in Escherichia coli isolated from Diarrheic and Clinically Healthy Suckling Calves in Sistan and Baluchistan Province, Iran

It is necessary to understand the frequency of virulence factor-encoding genes in the assessment of the carriage proportion. Moreover, it is required in the characterization of major unique antigens that are useful in the development of effective immunological-based preventive measures. The current study aimed to evaluate the frequency of three encoding-virulence genes associated with Enterotoxigenic (ET) and Shigatoxigenic Escherichia coli (E. coli/EC) pathotypes (k99, stx1, and stx2) in North of Sistan and Baluchistan Province, Iran. The frequency of k99, stx1, and stx2 was determined via polymerase chain reaction among E. coli isolates collected from the feces of the clinically healthy suckling (n=50) and diarrheic calves (n=50). The k99 gene was absent in all isolates, and the frequencies of the E. coli containing stx1 and stx2 or both stx1 and stx2 were estimated at 8%, 14%, and 4%, respectively, in the clinically healthy suckling calves (P>0.05), compared to 24%, 16%, and 6% in diarrheic animals (P<0.05). Among the three studied genes, there was a statistically significant difference between clinically healthy suckling and diarrheic calves in terms of the frequency of E. coli isolatescontaining stx1. On the other hand, the results of this study indicated that k99 was not a major fimbrial antigen-encoding gene in the ETECpopulation in the region. It is assumed that in any health measure intended to control the pathogen, other genes involved with encoding fimbriae should also be considered. The noticeable high frequency of E. coli isolates bearing stx1 and/or stx2 virulence elementsboth in clinically healthy and diarrheic suckling calves in this study isa concern for public health. Accordingly, it is recommended that further epidemiological studies be conducted on the role of the stx1 gene in the diarrhea of suckling calves in Sistan and Baluchistan Province, Iran.