RISK ASSESSMENT OF CASSAVA WASTEWATER FOR SURVIVAL, GROWTH AND DISSEMINATION OF SALMONELLA AND SHIGELLA ORGANISMS IN THE ENVIRONMENT.
Waste water samples from six cassava processing plants around Nsukka were cultured in MacConkey and Xylose lysine Deoxycholate Agar, after enrichment in Selenite F broth for isolation of Salmonella and Shigella species. Isolates were characterized using standard bacteriological techniques. Subsequently, soil samples were made acidic and/or supplemented with cyanide-containing waste water, to simulate conditions imposed by cassava waste water pollution, and then tested for support of growth of isolates. Salmonella (n=5) and Shigella (n=2) pathogens as well as other Gram negative bacterial pathogens (n=41) were identified among the bacterial isolates obtained. Further investigation from the cassava waste water and soil confirmed the presence of other microorganisms such as Bacillus spp., Pseudomonas spp., Corynebacterium spp., Aspergillus spp. and a lot of yeast cells. A microbial succession trend of the fermentation of a local variety of cassava was found with yeast strains, Candida pelliculosa, Candida tropicalis, Candida krusei, beginning and giving way to Bacillus spp. and then Corynebacterium spp. The pH of the fermenting cassava waste water decreased from 6.84 to 3.70. The isolates obtained from a medium of pH 3.00 includerd Arthrobacter spp., Bacillus spp., E.coli, Candida tropicalis and Candida pelliculosa. The survival and amplification of Salmonella typhi and Shigella dysenteriae strains in the two known variety of cassava (NR8082 and TMS 92/0326) were monitored by spectrophotometric method. The results show that cassava waste water, which is allowed to flood the environment, is a potential medium for growth and dissemination of Salmonella typhi and Shigella, and thus a potential risk for spread of typhoid and shigellosis in the community.