Contamination of Raw Eaten Lettuce with Pathogenic Salmonella, Aeromonas, Listeria and E.Coli at Production (Farm) and Market Sites in Urban and Peri-Urban Kumasi

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Some pathogenic microorganisms; Salmonella, Listeria, Aeromonas and co//, associated with urban vegetable production that uses wastewater for irrigation was assessed amongst smallholder urban and peri-urban farmers within the Kumasi r Metropolis. A total of 76 lettuce samples were collected under normal harvest and purchase conditions from some selected farm and market sites in Kumasi. The samples were analyzed for the presence and levels of Salmonella, Listeria, Aeromonas and E.coli using standard methods. Lettuce leaves from all the farms were contaminated and carried bacterial populations with mean values of 2.4 x 102, 3.6x 103, 8.1 x 102 and9.3 x 104 g"1 wet weight respectively for Salmonella, Aeromonas, Listeria and E.coli Lettuce from the markets were also contaminated with mean bacterial populations of 1.5 x 10 , 4.4 x 10 , 1.2 x 103 and 6.6 x 106 g-1 wet weight respectively for Salmonella, Aeromonas ^Listeria and E.coli. Levels of Salmonella, Aeromonas and E.coli on lettuce leaves at all the farm and market sites and of Listeria numbers at the Railways market did not meet the recommended PHLS guidelines making their consumption unacceptable and potentially dangerous to health. The levels of Aeromonas and E.coli on the lettuce leave samples at European market were higher than that of Gyenyase farms whiles that of Salmonella and Listeria recorded lower levels at European market compared to Gyenyase farms. Also bacterial numbers on lettuce leaves at Railways market were higher than that of Karikari farms with the exception of Salmonella that had lower numbers at the Railways market compared to Karikari farms. The study shows that although wastewater is a contributor to contamination of most and peri-urban produced vegetables sold and consumed in Kumasi there are other sources. Therefore using better quality water for irrigation may be desirable but not be sufficient safety procedure as it does not always ensure vegetables are of Salmonella, Aeromonas, Listeria and E.coli.
A Thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the award of the Master of Science degree in Environmental Science, 2007