Evaluation of Antibiotic Resistance Pattern of Gram-positive Bacilli Isolated From Ready-to-Eat Vegetables Sold in Ota Metropolis, Nigeria

Owolabi J. B, Ichoku C. K.


In most Nigerian cities, ready-to-eat (RTE) vegetables are purchased directly from street vendors and consumed immediately without necessarily having to cut, peel or rinse them as they have already been presumed to be processed by the vendors. However, the microbiological safety of these vegetables is of special concern due to the possible microbial contamination from incoming raw produce from farms, workers hygiene and handling practices, and the condition of the environment and equipment used to process the vegetables for distribution, marketing and sales. The aim of this study was to determine the incidence and antibiotic susceptibility patterns of Gram-positive Bacilli on RTE vegetables; Cabbage, Carrot, Cucumber and Lettuce from two local produce markets within Ota Metropolis. Pure cultures obtained by repeated streaking and identified based on cultural, morphological and biochemical characteristics were subjected to antibiotic susceptibility tests. The total aerobic bacteria present in the RTE vegetable samples Cabbage, Cucumber, Lettuce and Carrot ranged, respectively, from 1.84×106 - 2.24×106 cfu/g, 1.72 x106 - 2.48 x 106 cfu/g, 1.51x106 – 1.97 x 106 cfu/g and 1.69 x 106 – 2.42 x 106 cfu/g. A total of sixteen bacterial isolates from the RTE vegetables were tentatively identified as Bacillus brevis (30%), Nocardia spp. (18%), Bacillus spp. (12%), B. subtilis (12%), B. megaterium (6%), B. circulans (6%), B. sphaericus (6%) and B. pumilus (6%). Although, these bacteria are mostly causative agents of food spoilage and sometimes secondary infections, it is alarming that more than 80% of the bacterial isolates were resistant to at least two antibiotics including erythromycin, cloxacillin, cotrimoxazole, augmentin and streptomycin. The results of this study raise the spectre of antibiotic-resistance in normal soil microbes derived from RTE vegetables with potential impact on humans through the food chain and environmental exposure.

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