Pier Paolo Legnani

Legionella waterline colonization: detection of Legionella species in domestic, hotel and hospital hot water systems

Aims:  An evaluation was made of the prevalence of Legionella species in hot water distribution systems in the city of Bologna (Italy) and their possible association with bacterial contamination (total counts and Pseudomonadaceae) and the chemical characteristics of the water (pH, Ca, Mg, Fe, Mn, Cu, Zn and Total Organic Carbon, TOC).

Control of Legionella pneumophila contamination in a respiratory hydrotherapy system with sulfurous spa water.

OBJECTIVE To evaluate the effectiveness of different disinfection treatments in a spa water system contaminated by Legionella pneumophila and associated with a case of Legionella pneumonia. DESIGN During an 18-month period, the spa water was analyzed by taking samples from the well, the recirculation line, and the final distribution devices (nebulizers and nasal irrigators). Various attempts were made to eradicate Legionella organisms by chemical and thermal shock. The final protocol consisted of heat shock treatment at 70 degrees C-75 degrees C for 3 hours, 2 nights per week, followed by a lowering of the water temperature to 30 deg C+/-1 deg C for use in the plant. In addition, 3 times a week superheated steam (at a pressure of 1 atmosphere) was introduced for 1 hour into the nebulization machines. SETTING A spa at which sulfurous water was used for hydrotherapy by means of aerosol and nasal irrigation. PATIENT A 74-year-old woman with legionnaires disease. RESULTS After the case of infection occurred, L. pneumophila was isolated from the recirculation line at a concentration of 400,000 cfu/L and from the nebulizers and nasal irrigators at levels ranging from 3,300 to 1,800,000 cfu/L. The colonizing organisms consisted of a mixture of L. pneumophila serogroup 1 (12%) and serogroup 5 (88%). The shock treatment with chlorine dioxide and peracetic acid resulted in the eradication of Legionella organisms from the recirculation line but not from the water generated from the final distribution devices. After the restructuring of the plant and the application of thermal shock protocol, an evaluation after 12 months revealed no evidence of Legionella contamination. CONCLUSION To prevent Legionella colonization, disinfection treatment is effective if associated with carefully selected materials, good circuit design, and good maintenance practices.

Active Surveillance of Legionnaires Disease During a Prospective Observational Study of Community‐ and Hospital‐Acquired Pneumonia

A prospective surveillance study of legionnaires disease and an environmental survey of Legionella species were performed simultaneously in a general hospital. During a period of 3 years, 705 patients with pneumonia were screened with a Legionella urinary antigen test, and pneumonia was confirmed by culture and serological tests. Twelve cases of legionnaires disease were identified, none of which were hospital acquired, despite the fact that 60% of hospital water samples were contaminated with Legionella pneumophila at a concentration of more than 10(3) colony-forming units/L. The probable source of infection was identified for only 2 community-acquired cases. The results show that environmental contamination alone is not able to predict the risk of legionnaires disease. If no cases are present, monitoring of hospital water systems is of little significance; clinical surveillance is much more important.