ASSESSMENT OF THE ADSORPTION OF AEROMONAS HYDROPHILA ON POLYTHENE IN SODIUM HYPOCHLORITE AND HYDROGEN PEROXIDE TREATED WATER

A study was carried out on Aeromonas hydrophila adhesion to polythene fragment at different cell growth phases in aquatic microcosm. The main purpose of this study was to assess adsorption capacity, adsorption intensity and kinetics of Aeromonas hydrophila on polythene in sodium hypochlorite (NaOCl) and hydrogen peroxide (H2O2) disinfected water. The mean abundance of adhered A. hydrophila sometimes reached 28 and 111CFU.cm-2 respectively in NaOCl and H2O2 treated water. The adsorption capacities of A. hydrophila cells fluctuated between 1 and 2.12x1057 and between 1 and 2.29x1027 adhered cells.cm-2 in NaOCl and H2O2 disinfected water respectively. The adsorption intensities of this bacterium ranged from -45.81 to 3.49x1019 and from 0.16 to 2.29x1027 respectively in NaOCl and H2O2 treated water. Adsorption capacity and adsorption intensity of A. hydrophila cells on polythene in NaOCl treated water were greater than that obtained in water disinfected with H2O2. Adhesion kinetics of A. hydrophila cells oscillated between 0.001 and 0.930 adhered cell.cm-2.h-1. Adsorption kinetics seem resulted from interactions between bacterial cells and substrates, and depended both on the fragment type and bacterial species. The values of A. hydrophila surface hydrophobicity fluctuated between 65.11 and 92.74% in NaOCl disinfected water and between 63.38 and 89.41% in H2O2 treated water. The mean values of contact angle ranged from 83.1±0.6 to 85.8±0.8°.   Adhesion of A. hydrophila on polythene is mediated amongst others by cell growth phases, cell surface hydrophobicity, cell kinetic adhesion, adsorption capacity and adsorption intensity

Microbiological and physicochemical quality of some water points in the Nkolafamba Subdivision (Center Region, Cameroon)

A study was carried out with the objective of evaluating the microbiological and physicochemical quality of surface water in the  Nkolafamba subdivision, Center Region of Cameroon. Five sampling points were selected based on several criteria. The bacteria isolated were Mesophilic Aerobic Heterotrophic Bacteria (BHAM), bacteria that were witnesses to faecal contamination and Pseudomonas. Some abiotic parameters were measured using the usual techniques. The results show that some physicochemical parameters such as temperature was almost constant around 25 °C during the study period. There is also a pH which tended towards neutrality pH de (7,04 ± 1,03 U.C). However, it was noted that the stations are quite oxygenated (63,96%). Bacteriological analyzes revealed that an average value of 5.17 units (logUFC / 100mL) was recorded for BHAM. Overall, the abundances of total coliforms averaged 4.18 units (logUFC / 100mL). The waters of Nkolafamba also harbor a pathogenic microflora, with bacteria such as P. aeruginosa P. pasteurella, the abundance of which can sometimes reach 5,462 units (log CFU / 100mL). These germs can be the cause of eye infections or septicemia on users of these waters. These waters have a high bacterial load, and the microbiological pollution observed is predominantly animal. Some abiotic parameters such as pH, electrical conductivity, Suspended Solid (SS), nitrates and turbidity have influenced the distribution of these germs. The degradation of the quality of these waters is favoured by their proximity to sources of pollution, the runoff of contaminated water in the stations. These waters, without any treatment, are not recommended for human consumption according to the standards of the World Health Organization.Keywords: Abiotic variables, faecal coliforms, faecal streptococci, pathogenic bacteria, rivers

Synergistic effect of light, pH and Artemisia annua extract on Enterococcus faecalis in aquatic microcosms

International audienceSynergistic effect of abiotic and biotic factors is not completely established in the process of disinfecting water by plant extracts. The present study aims to evaluate the synergistic effect of different pH values (4, 5, 6, 7, 8 and 9) and different infusion concentrations (10, 20 and 30%) of Artemisia annua on Enterococcus faecalis growth in aquatic microcosm under dark and lighting conditions. The results showed that under dark condition, there was a relative increase in abundance of E. faecalis cells in the presence of A. annua extract. Under lighting, there is a decrease in the abundance of E. faecalis at different infusion concentrations of A. annua. Extract of A. annua seems to favour the growth of E. faecalis cells in the dark, especially at slightly acidic pH. This growth was relatively significant at pH 6. In the presence of light, A. annua extract inhibited the growth of E. faecalis cells and this varied from one extract sample to another; and was significant at slightly basic pH. Under the lighting, different pH values do not appear to have significant influence on the inhibition of bacterial growth except for pH 8. Monoterpenes, sesquiterpenes and triterpenes molecules present in infusions could be involved in chemical reactions responsible for cellular inhibition under light condition. Research on photosensitizing compounds and a comparative study with conventional photosensitizers might attest for the involvement of photosensitivity reaction with the A. annua extracts

Influence of Anthropogenic Pollution on the Abundance Dynamics of Some Freshwater Invertebrates in the Coastal Area of Cameroon

International audienceThe 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

Comparative Approach of the Antibiotics Susceptibility of some Bacterial Strains Concurrently Isolated from Raw Milk and Cattle Feed (Water and Fodder) from some Farms in the West Region of Cameroon (Central Africa)

International audienceFoodborne resistant bacteria have become a challenge to food security. Milk and milk products are easy vectors of transmission of foodborne pathogens, these being the main sources of human infection by antimicrobial resistant pathogens. The present study aimed at making a comparative approach of the antibiotic sensitivity/resistance of 3 bacterial strains (Escherichia coli, Salmonella spp. and Brucella spp.) isolated from milk, drinking water and green fodder consumed by cows in the West Cameroon region (Central Africa). Methodology: A total of 48 raw milk samples, 48 water samples and 48 green fodder samples were collected during the year 2020 and subjected to culture and identification of Escherichia coli, Salmonella spp. and Brucella spp. Antibiotic susceptibility testing was performed using the antibiotic disc diffusion method. Results: Escherichia coli isolates showed high resistance (56-100%) to ampicillin, amoxicillin/clavulanic acid, cefotaxime, ceftazidime and ceftriaxone in all three samples. Salmonella spp. isolates showed resistance to ampicillin only (62, 67 and 67%). Brucella spp. strains isolated from raw milk and drinking water showed high sensitivity (78-100%) to azithromycin, doxycycline, ciprofloxacin, levofloxacin, gentamicin, rifampicin and trimethoprim/sulfamethoxazole, streptomycin and tetracycline. Antibiotic sensitivity/resistance to Escherichia coli and Salmonella spp. strains largely did not differ between samples (P>0.05). No difference in sensitivity/resistance (P>0.05) of Brucella spp. strains isolated from milk and water was observed with respect to the 10 antibiotics tested. Conclusions: The emergence of resistance to various antibiotics commonly used in medical and veterinary practices has important implications for public health. It seems necessary to strengthen of the regulations covering the sale and prescription of antibiotics