Influence of Physico-Chemical Parameters on the Seasonal Dynamic of <i>Salmonella </i>spp Isolated from Urban Streams in Yaounde (Cameroon)

Abstract

As water resources in urban areas are becoming increasingly degraded, due in large part to poor sanitation, a study has been was conducted to examine the influence of physicochemical parameters and seasonal variation on the distribution of the enterobacteria <i>Escherichia coli</i> and <i>Salmonella </i>spp that have been isolated from the urban streams in the city of Yaounde. Bi-monthly water samples were collected from nine rivers during 12 months (April 2010 to March 2011). The isolation of bacterial germs was done according to the classical method. Physicochemical parameters were analyzed according to Standard methods. <i>Salmonella </i>spp was detected all over the studied year with a high prevalence of 49.4%. This prevalence varies from one season to another. <i>Escherichia coli</i> ranged between 2.5 x 10<sup>3</sup> to 67.1 x 10<sup>3</sup>UFC/100ml with highest prevalence observed during the long dry season. Physicochemical parameters revealed neutral to slightly alkaline waters (pH6.7 – 8.8), with low mineralization (EC= 126 – 743 µS/cm). Dissolved oxygen was generally less than 4 mg/l. Physicochemical parameters also showed temporal homogeneity in most of the variables (pH, EC, TDS, total hardness, alkalinity, Na, K, Mg, Ca). None of the physicochemical environmental variables analyzed had any specific influence on the presence of <i>Escherichia coli</i> or <i>Salmonella</i>. Furthermore, there was no significant correlation between the presence of <i>Escherichia coli</i> and <i>Salmonella </i>spp, as the sources of <i>Salmonella</i> spp contamination are probably different from those of <i>E. coli</i>. The observed pollution of rivers is related to the large anthropogenic activities in particular, the multiplicity of small farming closed to markets and houses, and husbandry activities along the streams which are important sources of organic matter. These rivers constitute a pool of <i>Salmonella</i> that can be easily disseminated in to different ecological systems and therefore represent a serious health risk for people who may come into direct or indirect contact with this pathogen.