Correlation of subtypes of Legionella pneumophila defined by monoclonal antibodies with epidemiological classification of cases and environmental sources.

Twenty-five clinical isolates of Legionella pneumophila serogroup I were classified as epidemic or sporadic on epidemiological grounds. All were isolated from patients at the Medical Center Hospital of Vermont (MCHV) in Burlington between 1977 and 1983. These coded isolates were examined with a panel of eight monoclonal antibodies to serogroup 1 and an indirect microimmunofluorescent test. Strains from 14 of the 15 MCHV epidemic cases had one staining pattern (A); isolates from eight of nine MCHV sporadic (nosocomial) cases had a different pattern (B). One sporadic strain was of staining pattern A, and in one epidemic case an isolate of each pattern (A and B) was obtained. The only case that was clearly community-acquired displayed a third staining pattern (C). Four isolates from the cooling tower considered the most likely source for the epidemic strains had an antigenic reaction identical to isolates in epidemic cases, whereas three strains from the potable water system displayed an antigenic pattern identical to isolates in sporadic cases.