[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.


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 atypical 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.


CONCLUSIONS
The most outstanding data in this subgroup of patients were: male-sex, smoking, atypical clinical manifestations and low mortality. The low virulence of this molecular genotype of L. pneumophila may be responsible, in part, for the low mortality observed in the outbreak in Murcia.
Gómez
Joaquín
J
Servicio de Enfermedades Infecciosas, Hospital Virgen de la Arrixaca, Universidad de Murcia, Murcia, Spain.
Mòdol
Josep
J
García-Núñez
Marian
M
Baños
Víctor
V
Lorenzo
Manuel
M
Pedro-Botet
María Luisa
ML
Hernández
Tomás
T
Herrero
José Antonio
JA
Ruiz
Joaquín
J
Sabrià
Miquel
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D016952:Legionella pneumophila / Q000472:pathogenicity*; D007877:Legionnaires' Disease / Q000453:epidemiology / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies