Impact of heavy metal residues on the diversity of bacteria isolated from a few water points in areas of agricultural activity

A study aimed at evaluating the impact of heavy metal residues on the diversity of bacteria of the Vibrio and Salmonella genera in surface and groundwater in agricultural activity zones was conducted from January to July 2021. The microorganisms sought were the bacteria of the Vibrio and Salmonella genera. These bacteria were isolated from twelve (12) groundwater points and four (04) surface water points by the surface spreading technique and that of filter membranes on Thiosulfate Citrate Bile Sucrose (TCBS) and Salmonella - Shigella media. (SS) for Vibrio and Salmonella respectively. Some abiotic parameters like heavy metals (Lead, Mercury, etc.) were evaluated using the usual techniques.

The results show variations in the concentrations of certain heavy metals such as zinc and copper. The most identified heavy metals are zinc (59%) and copper (40%), which would be due to the use of agricultural inputs in this area. Bacteriological analyzes revealed that these waters have a high and varied bacterial load. Densities of pathogenic bacteria reached an average of 4.10 2 CFU/100mL for Vibrio and 7.32.10 3 CFU/100mL for Salmonella. These germs can be at the origin in this commune of the epidemics of cholera and typhoid. Highly significant correlations (P<0.01) between bacterial abundances and copper were observed. The degradation of the quality of these waters is caused by their proximity to sources of pollution. According to European Union standards, these waters are not recommended for human consumption without any prior treatment.