Moïse Nola

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

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 Log10CFU/mL. All strains were able to survive/grow in used microcosms, and a maximal concentration of 5.61 Log10CFU/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 Log10CFU/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 Log10CFU/mL) and well W2 (2.09 Log10CFU/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.

Physicochemical water quality of the Mfoundi River watershed at Yaoundé, Cameroon, and its relevance to the distribution of bacterial indicators of faecal contamination.

Water quality of the Mfoundi River and four of its tributaries was studied by assessing some physicochemical variables (temperature, pH, conductivity, chlorides, phosphates and nitrogen ammonia, dissolved oxygen and carbon dioxide, organic matter content and Biological Oxygen Demand) and their influence on the distribution of bacterial indicators of faecal contamination (total coliform, faecal coliform and faecal streptococci). For this, standard methods for the examination of physicochemical parameters in water were followed, and statistical analysis (Pearson correlations) used to establish any relationships between physicochemical and biological variables. Our results revealed that almost all of the examined physicochemical variables exceeded World Health Organization (WHO) guidelines for recreational water. This was in agreement with a previous microbiological study indicating that these waters were not safe for human use or primary contact according to water quality standards established by the WHO. Results of our correlation analysis suggested that physicochemical and biological variables interact in complicated ways reflecting the complex processes occurring in the natural environment. It was also concluded that pollution in the Mfoundi River watershed poses an increased risk of infection for users and there exists an urgent need to control dumping of wastewater into this watershed.

An annotated checklist of freshwater stygobiotic crustaceans of Africa and Madagascar

In this study a checklist of the stygobiotic crustaceans specifically for Africa is provided for the first time. Several nomenclatorial and taxonomic changes, as well as many new species or localities, have been included in the list since the publication of Stygofauna Mundi (Botosaneanu, 1986), which deeply modifies our knowledge on the biogeography of Africa. The annotated checklist comprises 280 stygobiotic species of crustaceans belonging to 9 orders, 32 families and 103 genera. Information about the endemism and the biogeographical distribution is provided for each of the systematic orders.

Involvement of cell shape and flagella in the bacterial retention during percolation of contaminated water through soil columns in tropical region.

Microorganisms’ retention in soil contributes to the natural purification of groundwater. Bacteria found in groundwater are generally of various shapes. The aim of this study was to assess the importance of cell shape and flagella in bacterial retention during polluted water percolation through two soil columns CA and CB, in the equatorial region in Central Africa. Percolation tests were carried out using different water loads samples which were contaminated by Escherichia coli (straight rods, peritrichous flagella), Vibrio parahaemolyticus (rods bacteria, polar flagella), and Staphylococcus saprophyticus (spherical, free-flagellum). It has been noted that showed that through soil column CA, the mean values of cells retention ratios (TR ) varied with bacteria species considered, and from one applied water load sample to another. E. coli T R and that of S. saprophyticus were not significantly different (P> 0.05) for the two soil columns. V. parahaemolyticus TR significantly differed from that of E. coli and S. saprophyticus through soil column CA (P< 0.01) when the highest water load was applied, and through soil column CB (P< 0.05) for each of water load applied. A relative hierarchical arrangement of retained cells based on the TR showed that V. parahaemolyticus was less retained through the 2 soil columns. S. saprophyticus in most cases was more retained than others. The physical properties of the bacterial cell must be taken into consideration when evaluating the transfer of bacteriological pollutants towards groundwater.

Assessment of the hierarchical involvement of chemical characteristics of soil layer particles during bacterial retention in Central Africa

The main purpose of this investigation was to rank, in hierarchical order, some soil chemical factors that impact the sorption parameters of fecal indicator bacteria and Salmonella sp, during their transfer from soil surface to the groundwater table. Sorption coefficients (Kf) and linearity exponents (Ϫ) were obtained using the Freundlich isotherm. When Salmonella sp was present alone, the values of Kf varied from 2.70 log units mg−1 to 7.84 log units mg−1 of soil, and Ϫ varied from 0.04 to 2.70. When the two fecal indicator bacteria were present, Kf varied from 0.48 log units mg−1 to 8.53 log units mg−1 of soil, and Ϫ varied from 0.06 to 1.19. When fecal indicator bacteria and Salmonella sp were mixed, Kf varied from 1.73 log units mg−1 to 7.70 log units mg−1 of soil, and Ϫ varied from 0.09 to 0.88. The predominant factors controlling each sorption parameter varied with respect to soil layer and the bacterial species involved.

Photoinactivation of Staphylococcus aureus and Vibrio parahaemolyticus in the model aquatic microcosm: effect of light intensity and dissolved biodegradable organic compound

The impact of light (1,000 × 100,000 lx) on the inactivation of S. aureus and V. parahaemolyticus has been assessed under different concentrations of dissolved biodegradable organic compound (BOC) at pH 7.0. First, a gradual decrease in the number of cultivable cells was observed. Secondly, a cell reactivation was observed and it was marked in the absence of BOC. In the absence of BOC, the lowest value of cell inhibition rate (CIR) during the first 3 h was 0.138 h(-1) for S. aureus and 0.218 h(-1) for V. parahaemolyticus. In the presence of 10,100 and 1,000 mg/l of BOC, it was 0.196 h(-1), 0.243 h(-1) and 0.257 h(-1) for S. aureus respectively, and 0.285 h(-1), 0.306 h(-1) and 0.409 h(-1) for V. parahaemolyticus respectively. The CIRs values of each bacterial species significantly varied (P<0.001) with the changes in BOC concentration. In most cases, no significant difference was noted in the CIRs of both species when they were under the same light intensity and BOC. Nevertheless, it seems important to consider the impact of dissolved BOC during the treatment of bacterial polluted water.

Mixture of Sodium Hypochlorite and Hydrogen Peroxide on Adhered Aeromonas hydrophila to Solid Substrate in Water: Impact of Concentration and Assessment of the Synergistic Effect

The synergistic effects of the combined treatments of NaOCl and H2O2 on the elimination of A. hydrophila adhered to polythene under static and dynamic conditions were evaluated. The concentrations 0.1, 0.2, and 0.3‰ NaOCl and 0.5, 1, and 1.5‰ H2O2 were used. The contact periods were 180, 360, 540, and 720 minutes. The abundance of cells adhered reached 2.47 and 2.27 units (log (CFU/cm²)), respectively, under static and dynamic conditions after action of the mixture of disinfectants, whereas it reached 2.41 and 3.39 units (log (CFU/cm²)) after action of NaOCl and H2O2 alone, respectively. Increase in the incubation period resulted in a significant decrease in the abundance of cells adhered when the mixture of 0.3‰ NaOCl and 1.5‰ H2O2 was used (P < 0.01). For each cell growth phase, there was a significant difference amongst the mean densities of cells adhered after action of the mixture of disinfectants (P < 0.05). Although the Freundlich isotherm parameters relatively varied from one experimental condition to another, the K f value registered in the exponential growth phase was relatively higher in static state than in dynamic regime; cells adhered under dynamic condition seem more sensitive to the synergistic action than those adhered under static condition.

Contribution to the Study of Antibiotic Resistance on Salmonella and Shigella Strains Isolated in Central African Republic

Peoples are contaminated by germs such as Salmonella and Shigella. This contamination can occur either from the environment or by contact with infected animals on the farm. Peoples are frequently infected by the consumption of raw or undercooked meat, contaminated during the slaughter process [24]. Salmonella and Shigella are the leading cause of gastroenteritis food borne humans cause symptoms of a wide range of severity, usually manifested by a more or less severe diarrhea sometimes requiring therapeutic management [5-8]. In the absence of treatment, bacteremia or sepsis may also occur and be fatal, particularly for the elderly, children and immuno-compromised if no antibiotic is administered in time [9].

Adhesion of Escherichia Coli on Fragments of Some Environments Rocks in Aquatic Microcosm: Impact of PH and Biodegradable Organic Compound

A study was conducted in the laboratory to assess the capacity of rocks immersed in water to reduce the abundance of Escherichia coli and evaluated the impact of pH and, Biodegradable Organic Compound on adhesion process. These rocks have been chosen according to their representation in the aquatic environment and their chemical composition. The used rocks were collected in four different regions of Cameroon (Central Africa). Rocks used were granite, basalt, micaschist and sandstone. The pH of the medium ranged between 3 and 13 C. U, and Biodegradable organic compound (BOC) concentrations were 0, 2.5, 5, 7.5, 10 and 15 g/l. The duration of the cell adhesion varied from 180 to 1440 min. The highest acidic and basic pH very significantly increases the cells adhesion rate on the substrates (P E. coli cells adhered over time ranged from 8.5 x 10 3 ± 7.5 to 57.3 x 10 3 ± 11.2 CFU/cm 2 on the micaschist, 2.9 x 10 3 ± 3.1 to 81.8 x 10 3 ± 14.6 CFU/cm 2 on the granite, 3.9 x 10 3 ± 5.9 to 154 x 10 3 ± 18.1 CFU/cm 2 on the sandstone, and from 3.6 x 10 3 ± 5.2 to 184 x 10 3 ± 21.5 CFU/cm 2 on the basalt fragments. Therefore, these two parameters should be considered in the methods of treatment of drinking water.