BACKGROUND:The nontuberculous mycobacteria (NTM) have been found in different environmental sources. They tend to colonize different body surfaces and secretions. The purpose of this study is to evaluate the presence of NTM in the oral cavity of healthy individuals and its relationship to tap water or oral hygiene.MATERIALS AND METHODS:One hundred sixty-seven healthy subjects were recruited. Three consecutive early morning mouthwashes using tap water were performed and examined for the presence of Mycobacterium tuberculosis (MTB) and NTM. In addition we obtained mouthwashes from 30 control healthy individuals with good oral hygiene using sterile water and examined these for the presence of MTB and NTM.RESULTS:NTM was isolated from the mouthwash of 44 (26.3%) subjects that used tap water. On the other hand, NTM was isolated from the mouthwash of 10 (33%) subjects that used sterile water. Age, gender, social class oral hygiene and the regular use of toothbrush made no statistically significant differences in the isolation rate of NTM.CONCLUSION:The rate of isolation of NTM from mouthwash is high in normal subjects. It is independent of oral hygiene, the use of tap water or teeth brushing. Smear-positive sputum could be NTM rather than M. tuberculosis. Tuberculosis polymerase chain reaction or culture confirmation is essential in developing countries to avoid the unnecessary use of antituberculosis therapy when the clinical suspicion is very low.