Risk factors for atypical mycobacterial disease in patients with smear positive pulmonary TB

Non Tuberculous Mycobacteria (NTM) can cause severe infection in selected groups of patients and is very difficult to be differentiated from TB infection clinically or radiologically leading to miss diagnosis and wrong treatment in these cases, the Aim of the present study is to study risk factors associated with NTM disease in patients with Acid Fast Bacilli (AFB) smear positive, Subjects and methods: 1402 patients with AFB smear positive were included in the study, only 47 patients from the study group proved to have NTM disease (diagnosis was done according to ATS/IDSA criteria). Results: the mean age of the NTM patients was 61.8 ± 23.2 years, NTM was more common in older age groups and more common in white race patients, on using logistic regression analysis NTM disease was more commonly associated with old TB infection (42.6%) and with bed ridden patients on tracheostomy (31.9%). The most common organisms isolated were the MAC complex (55.3%) followed by M. Kansasii (34.04%). Conclusion: NTM disease should be put into consideration in patients with AFB smear positive and suffering from old TB infection or in bed ridden patients who are on tracheostomy, also if smear is positive for AFB and PCR is negative NTM should be suspected.