Detection, isolation and molecular characterisation of shigatoxigenic O157 and non-O157 Escherichia coli in raw and fermented camel milk.

Abstract

Prevalence and distribution of Escherichia coli O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC) in samples collected along raw and fermented camel milk marketing chain was assessed. A combination of culture media and immunomagnetic separation followed by typing for associated virulence factors and serotypes was performed. Thirty six percent (36%) of the isolates haboured either single or combinations of stx1, stx2 and eae with 77.7% being stx1-positive, 18.5% eae-positive, 3.1% stx1 and stx2- positive and 0.8% stx2 and eae-positive. The highest percentage (56.5%) of presumptive E. coli isolates was isolated from EMB agar while CHROM agar and CT-SMAC enabled the detection of 23 and 20.5% of isolates, respectively. However, 100, 38.6 and 12.3% of isolates from CT-SMAC, EMB agar and CHROMagar, respectively were found to be STEC. Serotypes O157, O111 and O113 represented 94, 2 and 4% of the STEC, respectively. A higher prevalence of STEC found in camel milk in the current study compared to milk samples in other countries from other animal species indicates that the milk could be an important vehicle for transmission of STEC to humans.