ABSTRACT
Non-0157 Escherichia coli, isolated from Nunu (fermented fresh cow milk) sampled from four major Nigerian cities, namely Abuja, Benin City, Lagos and Onitsha were investigated for the presence shiga toxins (stx1 and stx2) genes using PCR technique and for their verotoxigenic potentials using tissue culture assay on Vero cells. Result of the investigation reveal that out of the total 800 samples collected, 268 (33%) had E. coli and out of this, 217 (81%) had non-0157 E. coli. Total number of non-0157 E. coli isolated from the 217 samples was 503. Shiga toxin gene analysis of the isolates reveal that 199(40%) had stx1 gene alone, 192 (38%) had stx2 gene alone, 4(1%) had both stx 1 and stx 2 genes while 108 (21%) had none of the two genes. Tissue culture assay on Vero cells indicate that there is a strong relationship between the presence of stx genes and their degree of cytotoxic effect on vero cells as over 80% isolates without the genes exhibited weak cytotoxic effect whereas over 80% of those with the genes exhibited more than strong cytotoxic effect. The findings from this study provide evidence that presence of non-0157 E. coli in our food system can be of serious health challenge as sub-strains different from E. coli 0157:H7 have already been found in some other countries to be responsible for serious food borne infection outbreak.
Key words: Keywords: Non- 0157 Escherichia coli, Shiga toxins, Verotoxigenic, Nunu, Fermented Milk
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