Irrigation Water as Possible Source of Food Borne Pathogens in Raw Vegetables

Abstract

The effects of different sources of water on the microbial quality of raw leafy vegetables were studied. Two vegetables, lettuce (Lactuca sativa) and fluted pumpkin (Telfairia occidentalis) were planted in a sterile soil in the screen house, irrigated with rain, sewage-polluted stream, tap and well waters, for 60 days and harvested. Coliform and bacterial loads were counted on vegetable leaf surfaces and in the different water samples. The total bacterial counts of vegetable leaf surfaces ranged from 5.46log₁₀ cfu/g to 6.11log₁₀ cfu/g while coliform counts ranged from 0.00 to 5.43log₁₀ cfu/g. The total bacterial counts of the irrigation water samples ranged from 5.60log₁₀ cfu/ml to 6.12log₁₀cfu/ml while coliform counts ranged from 0.00 to 5.48log₁₀cfu/ml. Pathogenic bacteria observed in the samples were Escherichia coli, Staphylococcus aureus, Salmonella spp, Shigella dysenteriae, Klebsiella pneumoniae, Aeromonas hydrophila and Enterobacter aerogenes. This study shows that irrigation waters are possible sources of contamination of edible vegetables; therefore the irrigation of food crops with water of unknown microbial quality should be avoided.