Subserogrouping of 49 Legionella pneumophila Serogroup 1 Strains with Monoclonal Antibodies by Slide Latex Agglutination Method and Its Usefulness for Epidemiologic Study

Abstract

Legionella pneumophila serogroup (SG) 1 has been known as a most frequent and important causative bacteria of Legionella pneumonia. It was reported that antigenicity of the serogroup was composed by numerous antigenic factors. To study antigenic factor formula of Japanese isolates from both clinical and environmental sources together with Philadelphia 1 strain, we examined slide latex agglutination system with monoclonal antibodies for subsergorouping. Philadelphia 1 and GIFU10102 strain (environmental isolate) were used as immune strains based on a cross absorption test result by rabbit antisera. Five anti L. pneumophia SG1 monoclonal antibody-producing clones were established. All monoclonal antibodies were SG1 specific but showed different reactivities with strain to strain. We prepared monoclonal antibody sensitized latex and used for subserogrouping of isolated strains. Twenty-two clinical isolates from Legionella pneumonia patients and 26 environmental isolates were examined. Each strain was reacted with at least one of the 5 sensitized latex and its antigenic formula was designed by sensitized latex reaction pattern. As a total of 6 patterns demonstrated in clinical isolates and 7 patterns in environmental isolates, 48 L. pneumophila SG1 islates were divided into 11 subserogroup patterns. The antigenic formula of Philadelphia 1 was same as one of clinical isolate patterns. It was considered that this subserogrouping system would be a useful tool for epidemiologic study.