SENSITIVITY OF FLUOROCHROME MICROSCOPY FOR DETECTION OF MYCOBACTERIUM-TUBERCULOSIS VERSUS NONTUBERCULOUS MYCOBACTERIA

The results for 6,532 consecutive mycobacterial respiratory specimens collected from 1,040 patients from 1993 to 1995 in a Texas hospital we re studied to determine the sensitivity of fluorescence microscopy for detection of Mycobacterium tuberculosis and nontuberculous mycobacter ia (NTM). Smears were positive for acid-fast bacilli (AFB) in 63% (677 of 1,082) of specimens growing M. tuberculosis and 56% (638 of 1,148) of specimens growing the four most common species of NTM. Smear posit ivity by species was 58% (446 of 776) for iii avium complex, 51% (154 of 300) for rapidly growing mycobacteria (98% were M. abscessus), 78% (29 of 37) for M. kansasii, and 26% (9 of 35) for M. gordonae. Definit e or probable disease by clinical criteria was present in 79% of patie nts with M. avium complex, 93% of patients with rapidly growing mycoba cteria, 100% of patients with M. kansasii, and 0% of patients with M. gordonae. Patients with M. avium complex had a low incidence of AIDS ( 7%), and approximately 50% of non-AIDS patients had upper-lobe cavitar y disease and 50% had nodular bronchiectasis. Only 23 of 6,532 (0.35%) of AFB smears were positive with a negative culture excluding patient s on therapy for established mycobacterial disease, These studies sugg est that NTM are as likely as m. tuberculosis to be detected by fluore scent microscopy in specimens from patients from areas endemic for NTM lung disease and at low risk for AIDS.