Metal pollutants distribution within lake Victoria basin and their influence on the native and transient microbial flora
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Heavy metal concentrations in water and sediments in the rivers draining into the Lake Victoria were determined in this study. The metal levels were compared to the bacterial plate counts and bacterial resistance to commonly used antibiotics assessed. The samples were randomly collected from sewage outfalls and points bordering heavy metal activity settlements. Heavy metal analysis was done using Flame Atomic Absorption Spectrometer (F-AAS). The samples were assayed for native heterotrophic bacteria and coliforms. Sediment samples recorded a higher level of heavy metals with a mean range of 31.97-109.9, lead; 3.48-183.66, zinc; 3.01-17.03, nickel; 1.93-214.61, copper; 17.01-65.91, cobalt; and 2.08-25.89 mg/g chromium compared to water samples whose mean range was as follows;- lead; 0.77-0.94, manganese; 0.10-3.10, zinc; 0.23-1.16, cadmium 0.02-0.04, and copper 0.51-0.57 mg/l. The study showed a significant relationship in the amounts of heavy metals in water samples and the bacterial counts, r = 0.637, p < 0.05. 53.8% of the isolates showed multidrug resistance. The study showed no significant difference in multidrug resistance between the native heterotrophs and the coliform bacteria (F =1.75 P = 0.191 P > 0.05). However, multidrug resistance in heterotrophic bacteria (mean 46.52%) was higher than in coliform bacteria (mean 36.36%). Plasmid DNA finger print of the antibiotic resistant isolates showed a positive relationship between the plasmids carried and multidrug resistance. This could suggest that heavy metal pollution in wetlands induces multidrug resistance. The findings point to a potential health threat posed by heavy metal pollution to human and other forms of life in the aquatic ecosystems.