Low-nutrient R2A medium in monitoring microbiological quality of drinking water

Abstract

The possibility of using low-nutrient R2A medium for determining the total count of aerobic mesophilic bacteria was investigated. Sampling of water from particular points of water treatment and distribution at Krusevac drinking water treatment plant was conducted. The samples were inoculated simultaneously on Plate Count Agar (PCA) and R2A media, and incubated at 37 ?C and at room temperature. The bacterial count was determined after 48, 72, 120 and 168 h. The statistical analysis of the results showed significantly higher bacterial count on R2A medium compared to PCA. Moreover, a significantly higher bacterial count developed at room temperature compared to the temperature of 37?C. R2A medium recorded 3.6% of unsafe samples in the distribution system after the 7-day incubation at room temperature. On the basis of the obtained results, an optimum method for determining the total count of aerobic mesophilic bacteria for all investigated waters has been defined. The process of incubation is predictable and it can be described by a mathematical model in the form of a polynomial of the second or the third power.