Impact of Rainfall and Some Water Abiotic Factors on theAbundance Dynamic of Vibrio and Aeromonas Adhered toCopepods Surface in Some Coastal Streams and Rivers inCameroon (Central Africa)

International audienceA study was carried out on the tributaries draining into Rivers in the coastal region of Cameroon(Central Africa). It aimed at assessing the abundance of Vibrio and Aeromonas cells adhered to copepods withrespect to some considered abiotic factors. It has been noted that the tributaries are substantially concentratedin organic matter and these fluctuated, depending on the amount of rainfall received by the rivers throughoutthe period of the study. The abundance of Aeromonas cells adhered to copepod fraction ranged from 38CFU.Ind-1 to 8×103 CFU.Ind-1. That of Vibrio cells ranged from 75×102 CFU.Ind-1 to 42.4×103 CFU.Ind-1. Ofthe total bacteria identified in this study, V. cholerae relatively dominated the bacterial community (38%),followed by A. sobria (30%), A. hydrophila (27%) and other species namely V. alginoticus, V.parahaemolyticus, V. mimicus, V. vulnificus, A. cavia, Aeromonas sp. represented 5%. From the PrincipalComponent Analysis (PCA) assessing the influence of abiotic factors in the abundance changes of bacteriaattached to copepods, it appears that the first cloud of points includes the rainfall, pH, Aeromonas and Vibriowhile the second cloud on the left pole groups namely water temperature, salinity, carbon dioxide andoxydability. Vibrio and Aeromonas cells preferentially colonized copious quantities of copepods during theperiod of excess flood when the concentration of nutrients in the water column regressed. A complex network ofabiotic factors thus acts in synergy to influence the attachment of Aeromonas and Vibrio cells to copepods. Toprevent the risk of cholera outbreaks and non-cholera infections, ecological monitoring should be furtherenhanced during the period of excess rainfall

Comparative study of Moringa stenopetala root and leaf extracts against the bacteria Staphyloccocus aureus strain from aquatic environment.

International audienceThe present study assessed the abiotic factors of Moringa stenopetala (M. stenopetala) extracts against Staphyloccoccus aureus in aquatic microcosm. Bacterial survival was assessed using colony forming unit (CFU) method on culture agar medium at different concentration levels (0.5 to 2 g/L). The incubation duration varied from 3 to 24 hours, and the temperatures were between 7°C and 44°C. Phytochemical screening showed that most of the constituents obtained from the extracts are the alkaloids, flavonoids and the tannins. It was observed that increase in extract concentration significantly inhibited the number of CFU obtained. Compared to the control {9.27 Log(CFU/100 mL)}, cells abundance from different concentrations of leaves extracts fluctuated between 4.74 and 0 {Log(CFU/100 mL)} after 3h incubation; 5.46 and 0 {Log(CFU/100 mL)} after 6h; 4.75 and 0 {Log(CFU̸/100 mL)} after 9h, and 4.85 and 0 {Log(CFU/100 mL)} after 24h incubation. As for root extracts, the abundance were between 4.80 and 0 {Log(CFU/100 mL)} under 7°C incubation; 5.03-5.23 and 0 {Log(CFU/100 mL)} under 23°C and 37°C, and 4.66 and 0 Log (CFU/100 mL) under 44°C incubation when considering the whole extract concentrations used. Incubation temperature and extracts concentration significantly impacted bacterial abundances. When the decoction extracts of roots were used, the amount of S. aureus cells inhibited was registered after 3-24 hours incubation. The Pearson correlation coefficient in most cases, revealed an inversely proportional relationship between the plant extracts and S. aureus cultured cells in a dose-dependent manner (P≤0.05). The use of M. stenopetala extracts could constitute an alternative in the treatment of water intended for human consumption