Author(s)

ANIKÓ ZSENI, ROLAND MISETA, BÁLINT NÉMETH

Abstract

Using standard and routine methods for drinking water microbiological quality control may lead to uncertainty. In some cases, biochemical tests for confirmation of presumptive colonies have negative results. It can also happen that the target bacteria cannot be found, but the high concentration of the background biota contaminates water sampling points or even the entire water supply system. The aim of the study was to investigate and identify bacterial colonies retrieved from water samples of drinking water supply systems using a relatively cheap, fast and easy-to-use method as well as to acquire information on the presence of pathogens in the background biota. To achieve our goals, water samples from 18 western Hungarian settlements were collected during a two month period. A total of 66 morphologically different bacterial colonies growing on four media were tested for taxonomic identification by three different API (Analytical Profile Index) tests which are suitable for the identification of bacteria at species level. Out of the 66 bacterial colonies involved in the study, 58 could be identified by API tests. During the identification, the presence of 27 different taxa were proved in the water samples. As a result of our research, species (Aeromonas hydrophila, Pseudomonas fluorescens, Burkholderia cepacia) that can cause confusion in the evaluation of water samples by forming morphologically typical colonies on the medium or presenting in high number of colony form units as background contaminants were identified. The presence of species (Pseudomonas aeruginosa, Aerococcus viridans, Aeromonas hydrophila, Gemella morbillorum, Streptococcus constellatus) which originated from the background biota on different agar plates and can cause human diseases, were also confirmed. Even if the organisms which indicate water quality degradation are not present in the water sample, the background biota may contain human pathogenic bacteria that might lead to health problems when enriched in the drinking water supply system.

Keywords

microbiology, drinking water, API test, background biota, cultivation on agar medium.