Subtyping of Legionella pneumophila serogroup 1 strains isolated in Germany using monoclonal antibodies.

Legionella pneumophila serogroup 1 (Lp1) strains isolated from patients and hot water supplies in different locations of Germany were subtyped using seven monoclonal antibodies (mabs) in the indirect immunofluorescence test (IFA) and in part, using a dot blot assay. Four of these mabs were produced in Dresden. Three mabs (mab 33G3, mab 32A12 and mab 144c2) were kindly supplied by J. Joly, Quebec, Canada. Altogether, seven antigenic variants were found among Lp1 strains isolated in Germany. Patient strains belonged to the Philadelphia, Benidorm, Knoxville, France, Olda-Heysham and Bellingham subgroups, whereas environmental isolates reacted like the Bellingham, Oxford, Philadelphia, Knoxville and France strains. The majority of patient strains (15 out of 26, 58%) reacted with our mab 3/1 (corresponding to mab 2 of the standard panel), but only 26 out of 118 environmental strains (22%) isolated from 4 of 15 hot water supplies did so (p less than 0.05). The majority of water-borne Lp1 strains reacted with a mab specific of the Bellingham subgroup. Three water systems under study were associated with human legionellosis. Two of them contained Bellingham-like strains, one Philadelphia-like legionellae.