DENTAL UNITS - AN ENVIRONMENTAL-STUDY OF SOURCES OF POTENTIALLY PATHOGENIC MYCOBACTERIA

Setting: Infections caused by non-tuberculous mycobacteria (NTM) are g enerally thought to be acquired from environmental sources. However, l ittle is known about the situations in which transmission occurs. Obje ctive: In an attempt to identify situations of relevant contact with N TM we investigated the water to which patients are exposed during dent al treatment. Design: The concentration and species of NTM were determ ined in 43 cooling and spray water samples from 21 dental units in ten offices. In addition, mycobacterial colonization of 16 biofilm sample s from the waterlines of two dental units was investigated. Results: T he mean NTM concentration in the water samples was 365 colony-forming units (cfu) per mt, exceeding the mean drinking water concentration by a factor of almost 400. In the biofilm samples the mean NTM density a mounted to 1165 cfu/cm(2). The species identified included Mycobacteri um gordonae, M. flavescens, M. chelonae, 'M. chelonae-like organism' a nd M. simiae. Conclusion: High numbers of NTM may be swallowed, inhale d or inoculated into oral wounds during dental treatment, possibly res ulting in colonization, sensitization or infection. Mycobacterial prol iferation in biofilms forming within dental units may explain the exte nt of NTM contamination of dental spray and cooling water.