[The use of molecular epidemiologic markers in the study of an epidemic outbreak of legionnaires' disease of nosocomial origin]

Abstract

Background: Epidemiological investigations of Legionella infections are based, since recently, on molecular techniques that are more sensitive and specific than phenotypic traits. We were interested in these methods for subtyping isolates of L. pneumophila serogroup 1 and confirm the epidemic spread of an outbreak of legionnaires' disease at the Universitary Hospital Germans Trias i Pujol (HUGTiP) in Badalona.

Methods: Environmental samples taken from domestic water, heating and cooling water systems and oxygen humidifiers were examined. Clinical and environmental isolates of L. pneumophila serogroup 1 were compared by analysis of genomic DNA by restriction endonucleases.

Results: We could found L. pneumophila serogroup 1 and 9 in domestic hot water and heating systems and L. micdadei in cooling water system. Cleavage of genomic DNA showed that all restriction fragment patterns coming from clinical and environmental isolates of L. pneumophila serogroup 1 were identical and different from isolates belonging to the same species and serogroup but coming from community area.

Conclusions: Molecular analysis of clinical and environmental isolates of L. pneumophila serogroup 1 has allowed to identify a reservoir related to a nosocomial outbreak of legionnaires' disease at the HUGTiP, and a clonal population of L. pneumophila serogroup 1 in environmental samples genotypically identical to the clinical ones.