Epidemiologic study of nosocomial legionellosis by PCR & BCYE-α culture

Legionella sp. can contaminate the hospital water supply system, which may then act as a vehicle for acquisition of nosocomial legionellosis, occasio nally causing epidemics. Korea Univ. Guro-Hospital is tertiarly hospital with 600 beds, and there was no case of nosocomial legion ellosis before 1995. But 3 cases of legionella pneumonia were idenitified by culture of percutaneous lung aspirates from July 1995 to Aug. 1995. For epidemiologic study to define the source of nosocomial legionelbsis and to establish a preventive strategy, we performed BCYE-α culture and polymerase chain reaction with hospital-environmental water. A to tal of 20 samples from various sites of the hospital-water supply sys tern were prepared & polymerized with 5S rRNA primers. A 118-bp sized PCR product was produced from 8 samplest(PCR-positivity:40%). After hybridized with the digoxigenin-labelled probe, 9 bands (1 more band was produced, in addition) were obtained. The positive rates of PCR were especially high in the water samples from rooms, where the patients resided. But only in 3 samples, legionella sp. were cultured by BCYE -α (culture-positivity: 15%). After hyperchlorination of the water supply system, resurveillance (by culture & PCR) was performed in Aug. 1996. And there were neither positive results by culture & PCR from environmental water nor new patients. Therefore, annual surveillance of the hospital water supply system with legionella 5S rRNA PCR would be beneficial for early detection of contamination of the water supply system by legionella sp. and for prevention of nosocomial legionellosis.