Prevalence of Legionella species, serogroups, and monoclonal subgroups in hot water systems in south-eastern Germany.

To study the contamination of hot water systems in south-eastern Germany 75 houses were selected and water samples were collected from peripheral hot water taps, shower heads and in a few cases from central water storage tanks. A total of 661 water samples were cultured. 186 (27.7%) were positive for legionellae. In 68% of hospitals, 50% of outpatients departments, 58% of dental offices, 85% of public buildings and 65% of private households in large buildings legionellae could be isolated. Most samples contained legionellae in the range of 1-100 colony forming units (cfu) per ml, the highest concentration was 4000 cfu/ml. Isolated strains were typed using absorbed rabbit sera prepared against the ATCC-type strains by the indirect immunofluorescence test. Legionella pneumophila serogroup 1, 2, 5, 6, and 10 strains were further subtyped using monoclonal antibodies. A total of 1548 colonies were serotyped. If the same species, serogroup and subtype in a given water system was considered to be the same strain, 77 different strains were isolated. 31 buildings contained one, 11 buildings two, 3 houses three and one building six different strains. 72 strains belonged to the species Legionella pneumophila and 5 strains were non-pneumophila species. Legionella pneumophila serogroups 1, 3, 6, and 10 were most frequently isolated with 22%, 14%, 16% and 18%, respectively. Among the serogroup 1 strains, the monoclonal subgroup Bellingham was the most commonly found.