Low mortality rate in an outbreak of Legionnaires' disease: Correlation with the cytopathogenity study

Background: In 2001 an outbreak of Legionnaires' diseases occurred in Murcia, Spain, with one of the lowest known rates of associated mortality. We describe the clinical data of a subgroup of patients, and present the results from molecular and virulence studies to correlate the lower mortality of the overall series with the strain virulence. Patients and methods: A subgroup of 86 patients from the outbreak of Legionnaires' disease was prospectively included. Demographic, risk factors and clinical evolution data were obtained. Moreover, we performed a pulsed field gel electrophoresis and cytopathogenicity assay of the Murcia outbreak that were compared with other unrelated Legionella isolates. Results: Sixty-nine (77.9%) patients were males. The mean age of the patients was 58.2 years (range: 32-87). Smoking was the most frequent risk factor in 62 patients (71.7%) and 61 patients (70.2%) had underlying diseases. Clinical, laboratory and radiological manifestations were compatible with the a typical pneumonia syndrome. The mortality rate was 3.2%. All the clinical L. pneumophila isolates analyzed by PFGE showed the same subtype. When analyzing theses strains together with other Legionella strains, they were included in the group with lower virulence in the cytopathogenicity study.Copyright © 2008 Elsevier España, S.L. All rights reserved.