Contamination of dental simulation rooms with mycobacteria

Dental unit waterlines (DUWLs) often provide optimal conditions for pathogens, including non-tuberculous mycobacteria, causing various infections in patients and practitioners. Preventive measures for non-tuberculous mycobacteria (NTM) remain unclear. Dental simulation units, which are used for student training, are very similar to classic dental units. While the water quality of dental units has been the subject of numerous studies, dental simulation units have received little attention to date. In particular, there are very few studies on the role of NTM in dental simulation units and on influencing factors such as water stagnation, structural conditions, and the effectiveness of a disinfection program.

In this study, 24 dental simulation units from two rooms in two different buildings of the Department for Operative Dentistry, Periodontology and Preventive Dentistry were examined for NTM. Water samples were analyzed from all simulation units, and biofilm swabs were additionally examined from room 2. All samples were incubated on solid and liquid culture media for 8 weeks. The species of NTM were identified using GenoType line probe assays.

NTM were detected in 43 of 44 samples. Three different species were identified: M. gordonae was the most common, with 24 detections, followed by M. chelonae with 17 detections and M. chimaera with 3 detections.

The high contamination rate of dental simulation units highlights the need for further research to ensure a safe environment. No significant differences in terms of structural conditions could be found, while the influence of water stagnation and disinfection protocols warrants further investigation.