Significance of respiratory isolates of Mycobacterium avium complex in HIV positive and HIV negative patients

Abstract

Objective: Mycobacterium avium complex (MAC) is isolated with increasing frequency from respiratory specimens. This study was an attempt to determine the significance of this in human immunodeficiency virus (HIV)-positive and HIV-negative patients. Methods: A retrospective cohort study was conducted at Bellevue Hospital, a large municipal hospital in New York City, including all patients with two or more respiratory tract specimens positive for MAC during the period January 1996 to October 1996. Results: Eighty patients met inclusion criteria. Forty-six were HIV-positive, and 34 were HIV-negative. Age, gender distribution, and race were comparable. Cough was a common complaint in all patients, whereas HIV-positive patients were significantly more likely to have fever (19 vs. 2, P < 0.0001). Abnormal chest radiographs were common in both groups (P > 0.8), although HIV-positive patients were more likely to have diffuse abnormalities (P < 0.0001). Focal radiographic findings were similar for both groups; however, there was a trend toward more lymphadenopathy in the HIV-positive group, though this did not reach statistical significance (P = 0.17). Notably, patients in both groups frequently had an established concurrent pulmonary diagnosis or evidence of disseminated MAC infection. Patients who were HIV-positive had Pneumocystis carinii pneumonia (n = 10), pneumonia (n = 10), and disseminated MAC disease (n = 12); whereas the concurrent disease in HIV-negative patients predominantly was active tuberculosis (n = 13). According to the recent American Thoracic Society-recommended criteria for the diagnosis of pulmonary disease caused by nontuberculous mycobacteria only 7 of 46 HIV-positive patients and 1 of 34 HIV-negative patients met clinical, bacteriologic, and radiographic criteria for pulmonary disease caused by MAC (P = 0.052). Conclusion: Mycobacterium avium complex often is cultured from patients with other lung diseases, and its presence in sputum infrequently signifies true disease, though it is more likely to do so in HIV-positive patients.