Legionella monitoring: a continuing story of nosocomial infection prevention.

Of 21 cases of legionellosis, 14 were of nosocomial origin and 6 others had a possible nosocomial source. The hot and cold water systems, respiratory therapy equipment, puddles of rain water on flat roofs and in gutters, and demineralized water systems were all excluded as a source of nosocomial infection. By subtyping it was shown that Legionella pneumophila serogroup 1 isolates from 11 patients and from the cooling towers were indistinguishable.