Use of the direct and cultivation methods in the bacteriological examination of water in water supply system
2011
Ćirić, S., Faculty of Agriculture, Lešak (Serbia) | Ilić, Z., Faculty of Agriculture, Lešak (Serbia) | Milošević, B., Faculty of Agriculture, Lešak (Serbia) | Spasić, Z., Faculty of Agriculture, Lešak (Serbia) | Stojković, J., Faculty of Agriculture, Lešak (Serbia)
Bacterial abundance in the water used for drinking by humans and animals is a parameter that is closely linked to their health. Therefore, application of a method of detection of bacterial count which will indicate the real status of this parameter, as authentically as possible, is necessary. The bacterial load of water in certain stages of water supply using direct and cultivation methods was investigated. In the cultivation method, the water samples were inoculated on PCA and on R2A medium, and incubated for 7 days at 37 deg C and at room temperature. Direct method included filtration of samples stained with acridine orange and counting of bacteria on the filters under the epifluorescence microscope. Cultivation and direct methods showed the lowest bacterial count in the tank of Bagdala II, 0 cfu/ml and 611 bacteria/ml, respectively, and maximum abundance in raw water, 157 cfu/ml and 1,378,698 bacteria/ml, respectively. Statistical analysis showed that significantly higher count of bacteria was recorded on R2A medium compared to PCA, and at room temperature than at 37 deg C. By index TBC/AMB, the native raw water was classified as more polluted water when applying the results obtained at room temperature compared to the results obtained at 37 deg C. The most realistic bacteriological status of all water types was obtained using the direct method of quantification of bacteria. However, for routine monitoring of water in water supply system, as well as for the examination of bacterial regrowth in the distribution network, it is the best to apply the cultivation method which involves inoculation of samples on R2A medium and incubation at room temperature.
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