Relative abundance and diversity of staphylococci in some surface and underground water points in Yaoundé (Cameroon, Central Africa)

Abstract

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.