Abstract
BackgroundWorldwide, L. pneumophila sg 1 is the most common agent of Legionnaires’ disease ( 80 to 90% of the reported cases). In contrast, L. pneumophila sg 2–14 account for only 15 to 20% of community-acquired cases, although they account for over 50% of the environmental isolates. The discrepancy between environmental isolates and clinical cases of disease suggested that there are differences in virulence.We decided to subtype the environmental Legionella strains isolated from health care facilities (HCFs) and to compare the distribution of strains with the occurrence of hospital-acquired legionellosis.MethodsObservational ecological study based on the data provided by the regional surveillance of legionellosis and on data obtained from hospitals environmental monitoring.Using the monoclonal antibody MAb 3/1 of the Dresden Panel we collected and typed environmental strains of L. pneumophila sg 1 obtained during routine testing in 56 health care facilities from 2004 to 2009.The results of the laboratory analyses of the environmental samples were compared with the number of cases that each health care facility reported during the study period.ResultsThe association between the type of colonisation (L. pneumophila sg 1 vs others serogroups) and the incidence of reported cases was statistically significant (p = 0.03 according to the χ2 test).Legionella strains with the virulence–associated epitope recognised by MAb 3/1 were isolated in 8 of the 26 HCFs colonised by L. pneumophila sg 1; 7 of the HCFs colonised by MAb 3/1-positive strains accounted for 85% of the cases of hospital-acquired legionellosis reported during the 6-year study period. There was a statistically significant association (p = 0.003) between the presence of cases and colonisation by MAb 3/1-positive Legionella strains.ConclusionThis study suggests that hospitals colonised by more virulent strains should be aware of the increased risk and consider the opportunities of increase their monitoring efforts and implement more effective contamination control strategies.
Highlights
Worldwide, L. pneumophila sg 1 is the most common agent of Legionnaires’ disease ( 80 to 90% of the reported cases)
Based on the analysis of the strains isolated during environmental monitoring in the study period, the health care facilities (HCFs) were classified as 1) facilities contaminated by L. pneumophila sg 1 alone or in association with other Legionella serogroups or species (26/56) or 2) as facilities contaminated by one or more L. pneumophila serogroups alone or in association with other Legionella species (30/56)
Comparing the environmental data with the number of hospital-acquired legionellosis it emerges that 2 HCFs colonised with L. pneumophila sg 1 alone reported 10 cases; 5 HCFs that were not colonised with L. pneumophila sg 1 reported 6 cases, the remaining 9 HCFs colonised with several serogroups (L. pneumophila sg 1 and others serogroups) reported 71 cases
Summary
L. pneumophila sg 1 is the most common agent of Legionnaires’ disease ( 80 to 90% of the reported cases). Legionella pneumophila serogroup 1 is the most common cause of legionellosis, a sporadic and endemic disease that may be acquired from different environmental sources [1]. Two different strategies for preventing hospital-acquired Legionella pneumonia have been advocated. We reported [6] the findings of a two-year prospective study on the incidence of nosocomial legionellosis in hospitals contaminated with L. pneumophila other than serogroup 1 or non-Legionella pneumophila species. In the hospitals that only performed regular ordinary maintenance without carrying out decontamination measures, the results (32 hospitals, 325,703 patients, only one case of healthcare-associated Legionnaires’ disease reported) confirm that the presence of Legionella in a hospital’s water distribution system does not necessarily lead to legionellosis [7,8], and in hospitals contaminated with L. pneumophila non-sg 1, the risk of developing legionellosis is very low
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
