title: Legionella control in the water system of antiquated hospital buildings by shock and continuous hyperchlorination: 5 years experience.
abstract: BACKGROUND
  To control the presence of Legionella in an old hospital water system, an integrated strategy of water disinfection-filtration was implemented in the university hospital Umberto I in Rome.
  
  
  METHODS
  Due to antiquated buildings, hospital water system design and hospital extension (38 buildings), shock hyperchlorination (sodium hypochlorite, 20-50 ppm of free chlorine at distal points for 1-2 h) followed by continuous hyperchlorination (0.5-1.0 mg/L at distal points) were adopted, and microbiological and chemical monitoring of the water supply was carried out in the university hospital (December 2006-December 2011).
  
  
  RESULTS
  Overall, 1308 samples of cold <20°C (44.5%), mixed ≥20°C ≤ 45°C (37.7%) and hot >45°C (17.8%) water were collected, determining residual free chlorine (0.43 ± 0.44 mg/L), pH (7.43 ± 0.29) and trihalomethanes (8.97 ± 18.56 μg/L). Legionella was isolated in 102 (9.8%) out of 1.041 water samples without filters (L. pneumophila sg 1 17.6%, L. pneumophila sg 2-14 28.4%, L. non pneumophila 53.9%), and in none of the 267 samples with filters. Legionella was recovered in 23 buildings out of 38 and 29 samples (28.4%) exceeded 103 cfu/L. When considering the disinfection treatment Legionella was isolated: before shock hyperchlorination (21.1%), 15 days after shock hyperchlorination (7.8%), 30 days after shock hyperchlorination (3.5%), during continuous hyperchlorination (5.5%) and without continuous hyperchlorination (27.3%). Continuous hyperchlorination following the shock treatment achieved >70% reduction of positive samples, whereas no continuous hyperchlorination after shock treatment was more frequently associated to Legionella isolation (OR 6.41; 95% CI 3.10-13.26; p <0.001). Independent risk factors for Legionella isolation were: residual free chlorine <0.5 mg/L (OR 13.0; 95% CI 1.37 - 123.2; p <0.03), water T° ≥20°C ≤ 45°C (OR 12.0; 95% CI 1.28 - 111.48; p <0.03) and no continuous hyperchlorination after shock treatment (OR 10.3; 95% CI 1.06 - 100.05; p <0.05).
  
  
  CONCLUSIONS
  Shock and continuous hyperchlorination achieved significant Legionella reduction, but effective chlorine levels (>0.5 < 1.0 mg/L) deteriorated water quality (organoleptic and chemical). However, shock and continuous hyperchlorination remains a valid-term option in old buildings with no water system rational design, managing problems due to hospital extension and absence of a proper hot water recirculation system.
authors.affiliation: Department of Public Health and Infectious Diseases, "Sapienza" University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy. giovanni.orsi@uniroma1.it.
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: Orsi
authors.forename: Matteo
authors.initials: M
authors.lastname: Vitali
authors.forename: Lucia
authors.initials: L
authors.lastname: Marinelli
authors.forename: Veronica
authors.initials: V
authors.lastname: Ciorba
authors.forename: Daniela
authors.initials: D
authors.lastname: Tufi
authors.forename: Angela
authors.initials: A
authors.lastname: Del Cimmuto
authors.forename: Paolo
authors.initials: P
authors.lastname: Ursillo
authors.forename: Massimo
authors.initials: M
authors.lastname: Fabiani
authors.forename: Susi
authors.initials: S
authors.lastname: De Santis
authors.forename: Carmela
authors.initials: C
authors.lastname: Protano
authors.forename: Carolina
authors.initials: C
authors.lastname: Marzuillo
authors.forename: Maria
authors.initials: M
authors.lastname: De Giusti
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D004203:Disinfection / Q000379:methods*; D006761:Hospitals; D006785:Hospitals, University; D006358:Hot Temperature; D006801:Humans; D007558:Italy; D007875:Legionella; D061214:Patient Safety; D012307:Risk Factors; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D002713:Chlorine