Full Length Research Paper

Occurrence of Escherichia coli O157 in a river used for fresh produce irrigation in Nigeria

V. N. Chigor ^1*, V. J. Umoh² and S. I. Smith³

¹Department of Microbiology, University of Nigeria, Nsukka, Enugu State, Nigeria.

²Department of Microbiology, Ahmadu Bello University, Zaria, Kaduna State, Nigeria.

³Molecular Biology and Biotechnology Division, Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria.

*Corresponding author. E-mail: vnchigor@yahoo.com or nnamdiva@yahoo.co.uk. Tel.: +2348036922106.

Accepted 17 February, 2009

   Abstract

Concerns about the persistence of Escherichia coli O157 in irrigation waters and its transmission to fresh produce makes investigation of irrigation waters imperative. The prevalence of this pathogen and seasonal levels of water quality parameters in Kubanni River were studied, using standard methods, over a 10-month period. Detection rate for E. coli O157 confirmed by slide agglutination was 2.1%. Faecal coliform counts (FCC) exceeded acceptable limits and was significantly higher in the dry season than during the rainy season (p<0.05). Remarkably, nitrate level was significantly higher in the rainy season than dry season (p<0.05). A significant (p<0.05) correlation was established between FCC and each of nitrate (r = 0.25), biochemical oxygen demand (r = 0.51) and electrical conductivity (r = 0.55). It was concluded that the Kubanni River represents a potential public health risk, being unfit for fresh produce irrigation. Perhaps, this is the first report on the isolation of E. coli O157 from water sources in Nigeria.

Key words: Escherichia coli O157, contamination, irrigation water, nitrate, fresh produce, surface waters.