[Outbreak of Legionnaires' disease in a restaurant in the Community of Madrid, Spain].

Background: on June 27, 2012, 46 cases of community- acquired Legionnaires'disease were detected in the Public Health Service area 8 of the Community of Madrid. All of them had been in the same restaurant of the city of Móstoles within the incubation period of the disease.

Methods: this is a descriptive study. Variables studied in the patients were: demographic data, medical history, symptoms, clinical course and diagnostic tests. For qualitative variables, frequencies and percentages were calculated. For quantitative variables, mínimum, máximum and average of values were calculated. In water samples taken on risk devices, we studied chlorine concentration, pH, temperatura and presence of Legionella.

Results: Legionella pneumophila Serogrupo 1, Subgrupo Pontiac Allentown/France was isolated from the water culture from the sand filter of the outside fountain's treatment plant; this result coincided with the strain isolated from respiratory samples of 4 patients. On the other hand, in biofilm samples obtained from the champagne bucket it was detected by PCR the presence of Legionella pneumophila whose gene sequencing was identical to that found in a respiratory sample of one patient.

Conclusion: Legionella pneumophila serogroup 1 subgroup Pontiac Allentown/France serotype 448 was isolated in water samples, and this Legionella coincided with the one isolated from respiratory samples of some patients. So, we could show the link between environmental risk factor and the disease. This link was also confirmed by genetic sequencing with PCR.