Prevalence of Mycobacterium avium complex in respiratory specimens from AIDS and non-AIDS patients in a San Francisco hospital

Over the past several years there has been a large increase in the recovery of Mycobacterium avium complex (MAC) isolates from respiratory specimens submitted to the clinical laboratory at San Francisco General Hospital (SFGH). This increase in MAC recovery correlates with an increase in the number of cases of acquired immunodeficiency syndrome (AIDS) in the community. Although it is well known that MAC is often isolated from patients with AIDS, the isolation of MAC from respiratory specimens is often attributed to contamination of the specimen with MAC organisms present in the environment. To determine whether the increase in MAC isolates recovered at SFGH was due to an increase in environmental contamination of specimens or to the increase in our AIDS patient population, we conducted a study of the prevalence of MAC in respiratory specimens from AIDS versus non-AIDS patients. Results of specimens submitted to the clinical laboratory at SFGH for culture of mycobacteria were reviewed over a 12-yr period, from 1977 through 1988. The prevalence of MAC in respiratory specimens from AIDS and non-AIDS patients was determined for 4 yr during this period: the pre-AIDS year 1977; the first year AIDS was reported in San Francisco, 1981; 1984; and 1987. In 1977 and 1981 the prevalence of MAC in respiratory specimens was less than or equal to 0.5%, and all MAC isolates were recovered from non-AIDS patients. In 1984 the prevalence of MAC in respiratory specimens for AIDS and non-AIDS patients was 6.5 and 0.3%, respectively, and in 1987, 8.8 and 0.3%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)