PREVALENCE OF ENTEROBACTERIACEAE IN FRESH VEGETABLES SOLD IN OPEN MARKETS IN BENIN CITY

ABSTRACT

 Vegetables are good sources of nutrients such as minerals, oil, vitamins and carbohydrates. These vegetables can be contaminated by microorganisms thereby causing spoilage and food-borne illnesses. The aim of this study was to determine the prevalence of Enterobacteriaceae in fresh vegetables sold in open markets in Benin City, Edo state. A total of thirty samples comprising of five fresh vegetables each were obtained from three open markets namely: New Benin, Oba and Uselu markets. All samples were serially diluted and inoculated on Nutrient agar and MacConkey agar. Bacterial isolates were identified by cultural, morphological and biochemical methods, thereafter the Enterobacteriaceae isolates were subjected to acid tolerance test at pH 3.0 and bile salt tolerance test at 0.3% bile salt concentration after 1 and 3 hours of incubation. The total heterotrophic bacteria count from this study ranged from 0.44 ± 0.80 × 10⁶ (Oba market) to 2.53 ± 0.43 × 10⁶ (Uselu market) cfu/g while Enterobacteriaceae count ranged from 0.02 ± 0.01 × 10⁶ (Uselu market) to 2.01 ± 0.04 × 10⁶ (New Benin market) cfu/g. Twelve isolates were identified in this study. They include Proteus mirabilis, Bacillus spp., Salmonella spp., Staphylococcus aureus, Staphylococcus spp., Escherichia coli, Entrobacter aerogenes, Citrobacter freundii and Klebsiella pneumoniae. Entrobacter aerogenes¹ had the highest occurrence of 12.89% while Proteus mirabilis had the lowest occurrence of 3.61%. For the acid tolerance test, Escherichia coli had the lowest percentage viability of 90% while Proteus mirabilis and Klebsiella pneumoniae had the highest percentage viability of 100% after 1 hour of incubation. Enterobacter aerogenes² had the lowest percentage viability of 81.43% while Salmonella spp. had the highest percentage viability of 100% after 3 hours of incubation. Results of the bile salt tolerance test showed that Enterobacter aerogenes² had the lowest percentage viability of 87.96% while Klebsiella pneumoniae, Proteus mirabilis and Escherichia coli recorded highest percentage viabilities of 100% after 1 hour of incubation. Salmonella spp. had the lowest percentage viability of 87.80% while Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes¹ and Citrobacter freundii had the highest percentage viability of 100% after 3 hours of incubation. The high bacteria counts in this study could be attributed to the poor hygienic practices at the farms and the markets such as improper handling and washing of vegetables with contaminated water in the markets. Therefore, there is the need for a proper public education on good food handling practices (washing vegetables with salt and clean water) in markets. Also, vegetable farmers should employ the use of pipe-borne water to irrigate their vegetables instead of water from wells and streams.