Legionella pneumophila serogroup 1 subgrouping by monoclonal antibodies--an epidemiological tool.

A panel of 10 monoclonal antibodies was used to subgroup 326 strains of Legionella pneumophila serogroup 1. All but two strains could be classified into three major subgroups named after their representative strains Pontiac 1, Olda and Bellingham 1. Of the 50 isolates from patients, 44 representing 32 separate incidents were of the Pontiac subgroup. This subgroup was also found in 16 of 18 buildings epidemiologically associated with Legionnaires' Disease. In contrast, strains of the Olda subgroup predominated in buildings where no infections had occurred. In 9 of the 11 incidents where isolates were available from at least one patient as well as from the suspected environmental source, the monoclonal antibody reaction patterns of strains from patients were identical to those of one or more of their environmental counterparts.