Epidemiologic investigation by macrorestriction analysis and by using monoclonal antibodies of nosocomial pneumonia caused by Legionella pneumophila serogroup 10.

A 67-year-old woman was hospitalized with an acute pneumonia of the left lower lobe. Legionella pneumophila serogroup 10 was cultured from two sputum specimens taken on days 18 and 20 and was also detected by direct immunofluorescence assay by using a commercially available species-specific monoclonal antibody as well as serogroup 10-specific monoclonal antibodies. Antigenuria was detected in enzyme-linked immunosorbent assays by using serogroup 10-specific polyclonal and monoclonal antibodies. In the indirect immunofluorescence test rising antibody titers against serogroups 1, 4, 5, 8, 9, 10, 14, and 15 were found in serum, with the highest titers found against serogroups 8, 9, and 10. L. pneumophila serogroups 10 and 6 and a strain that reacted with serogroup 4 and 14 antisera were cultured from both central and peripheral hot water systems of the hospital. Macrorestriction analyses of the genomic DNAs by pulsed-field gel electrophoresis showed that the isolate from the patient was identical to the serogroup 10 strains from the hospital hot water system. In contrast, the genomic DNAs of 16 unrelated L. pneumophila serogroup 10 strains showed 12 different restriction patterns. Monoclonal antibody subtyping revealed only minor differences in L. pneumophila serogroup 10 strains isolated from different sources. In conclusion, macrorestriction analysis is a valuable tool for studying the molecular epidemiology of L. pneumophila serogroup 10.