Examination of bacteriological status of surface fresh waters using direct and cultivation methods

The number of bacteria in surface waters reflects the current state of waters and their trophicity, and it is the first parameter that is affected by the anthropogenic contamination. Traditionally, quantification of bacteria in waters is performed using the cultivation methods. However, all these methods detect only cultivable bacteria; the results depend on the incubation conditions, and the results are obtained after several days. These deficiencies are solved by using direct methods. This work is the first bacteriological examination of the reservoir elije and its tributaries by using a direct method of quantification. Total of 343 samples of water from the reservoir and its tributaries were processed. In each sample, the count of aerobic mesophilic bacteria was determined using cultivation method was involving involved inoculation of samples on high-nutrient PCA medium and on low-nutrient R2A medium, and incubation for 7 days at room temperature. The total number of bacteria was determined by epifluorescence microscopy technique after filtration of samples previously stained with acridine orange. Using the cultivation methods, the highest number of bacteria was recorded in the river of Blata nica on R2A medium (56,535 CFU/ml), and lowest in the basin Vodozahvat on PCA medium (1,364 CFU/ml). According to the results from R2A, water belonged to the class of water of poorer quality compared to the results from the PCA. The results obtained by the direct method were correlated with cultivation methods. The significantly highest number of bacteria was obtained by epifluorescence microscopy, and the lowest on PCA medium. If the application of direct method for some reason is not possible, the real results of bacteriological state of surface waters can be obtained by inoculation of samples on R2A medium with adequate incubation conditions.