Opportunistic bacteria in dental unit waterlines: assessment and characteristics

Aim: The study aimed to determine qualitative and quantitative contamination of dental unit reservoir water with aerobic and facultative anaerobic bacteria, with regards to health risk to dental staff and patients. Materials & methods: The study material included water samples from 107 unit reservoirs. Conventional microbiological methods were used. The isolated bacteria were divided into three groups according to pathogenic mechanisms. Results: Dental unit water contamination was widespread. The isolated bacteria average concentration was 1.1 x 10(5) CFU/ml, with Ralstonia pickettii as the prevailing species (49.33%). The total potentially pathogenic bacteria were 54.54% of all the isolated bacteria. Bacteria causing infectious and invasive diseases constituted over one-half of this group, while allergizing and immunotoxic bacteria occurred in smaller quantities. Conclusion: The presence of over 50% potentially pathogenic microorganisms among the isolated bacteria and their very high concentrations call for the daily use of effective methods to reduce dental unit water contamination and health risk.