No abstract

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 (T(R)) 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 T(R) 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 T(R) 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.

This study aimed at assessing the impact of some wells abiotic factors on the antimicrobial susceptibility of Pseudomonas aeruginosa isolated. A total of 14 well waters of Douala and Yaoundé towns (Cameroon, Central Africa) were chosen. Fifteen antibiotics were used to test antimicrobial susceptibility with the majority belonging to β-lactam, aminoglycoside and quinolone groups. Result showed that in Douala, electrical conductivity of water ranged from 145.38 to 559.69 μS/cm in well, while in Yaoundé, it ranged from 172.5 to 710.2 μS/cm. Dissolved oxygen ranged from 2.5 to 5.5 mg/l and from 3.9 to 5.1 mg/l, respectively, in Douala and Yaoundé. Organic matter varied from 2.3 to 7.2 mg/l and 1.4 to 5.2 mg/l in Douala and Yaoundé, respectively. As for pH, it fluctuated between 5.56 and 6.66 CU and between 5.1 and 7.0, respectively, in Douala and Yaoundé. The sampled waters harbour multi-drug-resistant P. aeruginosa strains. About 20.40% of strains from wells in Yaoundé metropolis expressed resistance to at least 5 antibiotics, whereas from wells in Douala town, up to 33.33% of strains were resistant to at least 8 antibiotics including ticarcillin, ceftazidime and gentamicin. The effect of abiotic factors on the sensitivity to antibiotics was assessed using the multiple regression tests. In both towns, less than 5% in the changes of physicochemical parameters of well waters explained the variance in inhibition diameter values of antibiotics (p ≤ 0.05). The pH significantly impacts on antimicrobial susceptibility. Environmental conditions are less stressful for P. aeruginosa and fairly affect its antimicrobial susceptibility.

No abstract

The abundance dynamic of some freshwater invertebrates in relation with the abiotic factors of the medium was studied from March 2013 to March 2014 on the main streams of the Wouri and Sanaga basins. Individuals of Copepoda, Atyidae, Chironomidae and Physidae were collected, identified and counted. Samplings were carried out monthly; meanwhile measurements of the environmental variables were taken. Results of the physico-chemical analyses revealed that water of the Sanaga basin is globally well oxygenated (77% -92%) and faintly mineralized (14 -107 µS/cm), excepted in the stations receiving household pollutants. Inversely, in the Wouri basin, waters are hypoxic with high content of organic matters (27.79 ± 9.43 mg/L). During rainy season (June-September), there is a dilution-dispersion of the organic matter due to stormwaters. Concerning biological analyses, the families of Physidae and Chironomidae were more abundant in urban stations than in stations situated in suburban area, especially during low water level period, showing that they are well adapted to anthropogenic and organic pollutions. The hypoxic conditions of urban waterways do not favor the proliferation of sensitive taxa such as Atyidae and Copepoda. These taxa preferred well oxygenated waters with rapid flow, and are more abundant during rainy season in stations located in suburban area or which are less subjected to anthropogenic disturbances.