Screening for virulence genes in <i>Escherichia coli</i> O157:H7 obtained from drinking water from Ikara, Kaduna state, Nigeria.

Abstract

Eighty (80) sources of drinking water comprising boreholes (24), streams (3), wells (29), pipe-borne (5) and 19 sachet water samples were collected between March 2014 and February 2015. Escherichia coli (E.coli) O157:H7 was isolated by enrichment in Tryptone soy broth at elevated temperature and streaking on Eosin Methylene Blue agar. Typical green colonies with metallic sheen were Gram stained, after which biochemical tests and streaking on cefuxime-tellurite sorbitol MacConkey agar was done, followed by serological tests and by partial sequencing of the 16S rRNA gene were carried out to confirm the identity of the isolates. The isolates were screened for the presence of virulence genes (stx1, stx2, eaeA, hlyA) using the polymerase chain reaction (PCR) technique with specific primers. Three samples (2 wells and 1 stream) were found to be contaminated with E. coli O157:H7. None of the isolates possessed the stx1 gene, one carried the eaeA gene (229bp), while all three showed amplicons for the stx2 and hlyA genes (1181 and 534bp respectively). The 16S rRNA sequences were deposited in the National Center for Biotechnology Information GenBank under accession numbers KX602652, KX602653 and KX602654. The isolation of this organism possessing virulence genes from drinking water is of public health significance and therefore, more attention needs to be paid to drinking water of Ikara, Kaduna state.

Keywords: Drinking water, Escherichia coli O157:H7, PCR, virulence genes