Survival and Growth of Vibrio cholerae , Escherichia coli , and Salmonella Spp. in Well Water Used for Drinking Purposes in Garoua (North Cameroon)

Abstract

The ability of strains of faecal bacteria ( Vibrio cholerae , Escherichia coli ATCC 25922, and four strains of Salmonella isolated, resp., from well water, pig, poultry, and human urine in Garoua) to survive or grow in well water microcosms was compared. Water samples were obtained from two wells in Garoua (north Cameroun). Autoclaving at 121°C for 15 min and filtration through 0.2 µm filter were used to make microcosms. Microcosms were constituted of unfiltered-autoclaved, filtered-nonautoclaved, and filtered-autoclaved well waters. Bacterial strains were inoculated at initial cell concentration of 3 Log 10 CFU/mL. All strains were able to survive/grow in used microcosms, and a maximal concentration of 5.61 Log 10 CFU/mL was observed. Survival abilities were strain and microcosm dependent. The declines were more pronounced in filtered-nonautoclaved water than in the other microcosms. E. coli and Salmonella sp. (poultry strain) lowered to undetectable levels (<1 Log 10 CFU/mL) after two days of water storage. V. cholera decreased over time, but surviving cells persisted for longer period in filtered-nonautoclaved water from well W1 (1.91 Log 10 CFU/mL) and well W2 (2.09 Log 10 CFU/mL). Competition for nutrients and/or thermolabile antimicrobial substances synthesized by “ultramicrocells” or by the autochthonous bacteria retained by the filter might affect the bacterial survival.