Increase in Mycobacterium avium complex isolations among patients admitted to a general hospital

In early 1979, an official of an Illinois hospital reported an increase in the number of patients from whom Mycobacterium avium complex recently had been recovered. Over the preceding 3 years specimens from a total of 51 patients were culture positive for M. avium complex: 7 in 1976, 8 in 1977, and 36 in 1978. Nine of 10 serotyped isolated were serotype 8. The increase was not attributable to an increase in the number of mycobacterial cultures performed. No other area hospitals had similar increases in rates of recovery of M. avium complex. Patients with M. avium complex were significantly more likely than patients with other mycobacteria to have been residents of the city where the hospital is located. The distribution of abnormalities in patients' chest films differed significantly between patients with M. avium complex in 1978 and patients with M. avium complex in 1976-77; in 1978, patients although equally likely to have infiltrates, nodules, or cavities, were more likely to have no abnormalities or abnormalities consistent with chronic obstructive pulmonary disease, and less likely to have other abnormalities. The data suggest that the increased rate of recovery of M. avium complex from patients could not be attributed to ascertainment bias or laboratory variation but may be due to an increase in the incidence of disease or colonization among persons living in the community where the hospital is located.