Abundance of the bacteria Listeria during the great rainy and dry seasons in some wells and lake waters in an urbanized equatorial zone of Cameroon (Central Africa)
Bacteria of the Listeria genus are zoonotic pathogens responsible for listeriosis. This study aimed to investigate the abundance of Listeria in wells and lakes waters during the major rainy and dry seasons and assess the health risks faced by users. Samplings were carried out monthly on 4 wells and 4 lake water stations. Bacterial abundance was assessed using selective agar culture media. Physicochemical analyses indicated that wells are slightly acidic, contain lower dissolved dioxygen concentrations and higher content in dissolved CO2 levels than lake water, which was predominantly alkaline. In wells, abundance of Heterotrophic aerobic mesophilic bacteria (HAMB) varied from 2×104 to 89×105 CFU/100 mL during the rainy season, and from 4×104 to 8×105 CFU/100 mL during the dry season. That of Listeria varied from 6 to 14.5×102 CFU/100 mL during the rainy season, and from 1.28×102 to 20.5×102 CFU/100 mL during the dry season. In lakes, abundance of HAMB varied from 24×103 to 36×105 CFU/100 mL during the rainy season, and from 26×103 to 16×105 CFU/100 mL during the dry season. That of Listeria ranged from 40 to 4×102 CFU/100 mL during the rainy season, and from 98 to 41×102 CFU/100 mL during the dry season. Abundance of Listeria was negatively correlated with the water pH in wells during the rainy season, whereas with dissolved oxygen in lake during the dry season (P≤0.05). Dissolved CO2 seemed to favor Listeria abundance in lake during the dry season (P≤0.05). No significant difference in Listeria abundance was found between the rainy and dry season (P>0.05). The survival of Listeria in aquatic environment would greatly depend on factors other than those considered in this study. Despite the relative temporal variations in the abundance of the bacterial contaminant, the risk of listeriosis associated with the analyzed water appears unchanged with the season change.
