Potential Risk of Transmitting Escherichia coli O157:H7 through Some Vegetables Sold in Zaria Metropolis

Abstract

This study was designed to assess the potential risk of transmitting E. coli O157:H7 through vegetables. Suspensions (25g of vegetable in 225ml of distilled water) of 100 vegetables, 20 each of spinach, carrot, cabbage, lettuce and tomatoes were separately cultured on Eosine Methylene Blue Agar (EMBA) for the viable count and isolation of E. coli. The isolates characterized biochemically as E. coli were sub-cultured on Sorbitol-MacConkey agar which is selective for E. coli O157:H7. The efficacy of salt and vinegar in disinfecting the vegetables was examined on the E. coli O157:H7 isolates. Various concentrations of vinegar and salt were tested against E. coli O157:H7 using agar well diffusion method and tube dilution technique. Highest E. coli count was found in lettuce (22.0 x 104 CFU/g) with carrot having the lowest E. coli count (8.0 x 104 CFU/g). The prevalence of E. coli O157:H7 was 10% in spinach, 5% in tomatoes and 0% each for cabbage, carrot and lettuce. The minimum inhibitory concentrations (MICs) were 12.5% (v/v) and 0.0125g/ml and the minimum bactericidal concentrations (MBCs) were 50% (v/v) and 0.025% g/ml, for vinegar and salt respectively. Vegetables were found to harbor pathogens like E. coli O157:H7. Salt and vinegar are good disinfecting agents in washing the vegetables.