This study assessed the antibiotics susceptibility of Bacillus cereus, B. thuringiensis and B. subtilis strains isolated in wells and rainwater samples in Yaounde (Cameroon). Water samples in wells were collected monthly during a long dry season (LDS), a short dry season (SDS), a long rainy season (LRS) and a short rainy season (SRS), and during the LRS and the SRS for rainwater. The antibiotics considered included Imipenem, Amikacin, Gentamycin, Ciprofloxacin, Ofloxacin, Sulfamethazol, and Tetracycline. With strains from the groundwater, the antibiotic inhibition diameters varied from 9.13 mm (Sulfametazole during SDS) to 32.78 mm (Imipenem during LDS) with B. thuringiensis, from 8.2 mm (Sulfametazole during SDS) to 35.25 mm (Imipenem during LDS) with B. cereus, and from 5.05 mm (Ofloxacin during LRS) to 29.25 mm (Imipenem during LDS) with B. subtilis. With those from the rainwater, they varied from 4.55 mm (Sulfametazole during LRS) to 25.65mm (Imipenem during LRS) with B. thuringiensis, from 2.13 mm (Imipenem during LRS) to 20.05mm (Imipenem during SRS) with B. cereus, and from 5.03 mm (Gentamicin during SRS) to 25.15mm (Tetracycline during SRS) with B. subtilis. Bacillus strains isolated during LRS were multiresistant to the majority of antibiotics. The inhibition diameters of the most antibiotics varied significantly from one season to another (p<0.05).

The objective of this study is the phytochemical analysis and the determination of the antibacterial activity of aqueous and hydro-ethanolic extracts obtained from the leaves and bark of the trunk of Albizia zygia, against Escherichia coli and Salmonella typhi bacteria in aquatic microcosms. Phytochemical screening was performed as described by Pareck. The results obtained show that the hydro-ethanolic and aqueous extracts of Albizia zygia trunk bark recorded higher extraction yields (26.71% and 33.2% respectively) compared to the aqueous and hydro-ethanolic extracts of leaves of the same plant. Secondary metabolites with antibacterial activities such as anthraquinones, anthocyanins, flavonoids, polyphenols, tannins and saponins were found in both types of extracts. Flavonoids and anthocyanins were relatively more abundant than the other chemical constituents. The highest cellular inhibition rate of Escherichia coli was 99.88%, obtained after 9 hours of exposure in the hydro-ethanolic extract solution of trunk bark at the concentration 1.5 g/L.The Salmonella typhi rate was 99.95% after 9 hours of exposure of bacterial cells to the hydro-ethanol extract of the bark of the trunk at the concentration 1.5 g/L. This rate increased proportionally with the bacterial-extract contact time. The temperature of the medium did not significantly influence bacterial inhibition (P > 0.05). The obtained results justify the use of the plant Albizia zygia in the reduction of the flow of bacterio-pollutants contained in water

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A study aimed at evaluating the abundance and the diversity of staphylococci in surface and underground water points was carried out in the city of Yaoundé during the period from February to August 2020. The bacteria sought were heterotrophic bacteria aerobic mesophiles (BHAM) and staphylococci. They were isolated by the technique of surface spreading on a Petri dish on PCA (Plate Count Agar) and the membrane filter technique on Chapman mannitol medium (Mannitol Salt Agar), for BHAMs and staphylococci respectively. The bacteria isolated were identified by standard methods. Some abiotics parameters were measured according to usual analytical techniques. These analyses show that the abiotic variables have varied throughout from one sampling period to another and from one point to another. Thus, it was noted that the waters are acidic and not very mineralized. The high nitrogen and orthophosphate values recorded at all the sampling points testify to the richness of organic matter in the water analysed. Bacteriological analyses revealed that these waters harbor a high density bacterial microflora consisting of BHAM and bacteria of the genus Staphylococcus. In fact, concerning the BHAMs, their mean densities in CFU per 100 ml were 4, 42 and 4, 13 respectively in the Olézoa stream and the various wells. In addition, Staphylococcus aureus and Staphylococcus epidermidis are the different species of genus Staphylococcus found with an average density of 4, 26 log CFU/100 ml and 2, 79 log CFU/100 ml for Staphylococcus aureus and 1, 11 log CFU/100 ml and 2, 79 log CFU/100 ml for Staphylococcus epidermidis respectively in the Olézoa stream and the different wells studied in the Olézoa watershed. The densities of staphylococci in the wells were less abundant but more diversified than those in watercourse. Significant correlations were observed between these germs and parameters such as electrical conductivity, color, suspended matter, dissolved O2, dissolved CO2, PO43- and NH4+. The degradation of the quality of these waters is favoured by their proximity to the sources of pollution with sampling stations, the exogenous inputs and the poor maintenance of the wells. These waters without any treatment, are not recommended for human consumption according to the World Health Organization standards.