Distribution of Pseudomonas aeruginosa and Aeromonas hydrophila hydrophila in groundwater in equatorial zone in Cameroon and relationships with some environmental chemical factors
bacteriological and chemical study was carried out on the waters of four springs and six wells over 13 months and 12 months, respectively, in the town of Yaounde and its environs in Cameroon. For these groundwater points the study analysed the importance of pH, electrical conductivity, dissolved oxygen and carbon dioxide, and some ions such as sodium, potassium, calcium, magnesium, chloride and bicarbonate, for communities of Pseudomonas aeruginosa and Aeromonas hydrophila. The two bacteria P. aeruginosa and A. hydrophila are considered opportunistic pathogens. Different groundwater points were chosen on the basis of their spatial distribution and the size of the human population using them. Microbiological analyses were carried out by membrane filtration and chemical analyses were performed using standard analytical techniques. It has been noted that the monthly maximum abundance of P. aeruginosa and A. hydrophila varies from 1 to 22 x 103 CFU per 100 ml and from 1 to 7.8 x 103 CFU per 100 ml of water, respectively. These bacteria are sometimes rare and their abundance undergoes spatio-temporal fluctuations. The studied waters are slightly bicarbonate and soft, with a low to average level of mineralisation. The pH varied from 3 to 5 and the concentration of dissolved CO2 from 300 to 532 mg/l. Most chemical characteristics were relatively stable with time, but exhibited apparent spatial fluctuations. The level of correlation between the chemical parameters and the abundance dynamics of P. aeruginosa and A. hydrophila is heterogeneous. Depending on the origin (well or spring) of water samples and minimising their spatial variations, samples were grouped into single biotopes (either mother well or mother spring) which were separated into compartments. A correlation test was then carried out using data obtained from 52 monthly-average samplings in the four compartments of mother-spring water, and using data obtained from 72 monthly-average samplings in the six compartments of mother-well water. From this it emerged (P < 0.001) that in springs increases in pH, electrical conductivity, and in concentrations of chloride, sodium, potassium, calcium, magnesium and dissolved oxygen favoured the development of P. aeruginosa and A. hydrophila. High concentrations of dissolved carbon dioxide reduced (P < 0.001) the abundance of these bacteria. In wells, the ecology of P. aeruginosa and A. hydrophila is relatively unstable in comparison with springs. The higher instability in well water is ascribed to an increase in the number of confounding factors, which make wells appear more vulnerable than springs. This leads to the multiplication of asymmetrical interaction networks affecting bacterial population dynamics.