Prevention of nosocomial legionellosis by best water management: comparison of three decontamination methods

BACKGROUND

Since 2000, the National Health System has adopted international guidelines for assessing Legionella spp. in hospital water systems. The control of water contamination by Legionella spp. is still a matter of research concerning the most effective method in preventing nosocomial infections.

AIM

To compare three different decontamination methods by monitoring colony-forming unit count and number of hospital-acquired legionellosis cases. A secondary objective was to evaluate the long-term effects of the preventive measures on the water pipes.

METHODS

A protocol was developed for the selection of high-risk sampling sites and for the testing of three disinfection methods over the course of 19 years: hyperchlorination and thermal shock (period A, 2000-2005); copper-silver ionization (period B, 2006-2010); and integration of pre-filtering, filtering, pipe-protecting products, and remote control with chlorine dioxide (ClO₂) (period C, 2011-2018).

FINDINGS

The use of shock disinfection and hyperchlorination led to a decrease in contamination level immediately after the procedure, but then it rose again to the previous level in two months. Both copper-silver ionization and ClO₂ disinfection showed a stable and durable decrease in contamination level. Throughout these three phases, six cases of Legionella spp. occurred during period A, six cases during period B, and three cases during period C. With regard to the damage of water pipes, effective copper-silver levels caused corrosion and calcification in water pipes.

CONCLUSION

Both copper-silver ionization and ClO₂ properly controlled Legionella spp. contamination. ClO₂ significantly reduced the number of positive sites (P < 0.001) without damaging the pipelines.

Public Health and Hospitals: a Common Area for Clinical and Public Health Medicine

Contrary to what has happened so far, hospitals should become a setting which jointly exercise Clinical and Public Health Medicine. The areas of activity that require the presence of multidisciplinary teams and can bring benefits both to the patients and to the community is briefly described.