Epidemiology and Infection

Research Article

Relationship between Legionella spp. and antibody titres at a therapeutic thermal spa in Portugal

G. Rochaa1, A. Veríssimoa2, R. Bowkera3, N. Bornsteina4 and M. S. Da Costaa5 c1

a1 Faculdade de Medicina, Universidade de Coimbra, Portugal

a2 Departamento de Zoologia, Universidade de Coimbra, 3049 Coimbra Codex, Portugal

a3 Department of Biology, Alma College, MI 48801-1599, USA

a4 Centre National de Référence des Légionelloses, Faculté de Médecine A. Carrel, 69372 Lyon Cedex 08, France

a5 Departamento de Bioquímica, Apartado 3126, Universidade de Coimbra, 3000 Coimbra, Portugal


The presence of Legionella spp. in the water of a Portuguese spa was ascertained during the spa season, between May and November. Simultaneously the prevalance of anti-legionella antibodies in people attending the spa was also investigated. The antibody titres of 172 randomly selected patients and 42 therapists were determined, and compared with a control group of 503 blood donors. Legionellae were present in the spa water at low concentrations, generally lower than 103 c.f.u./1. A total of 92 strains representing eight different species or serogroups were isolated; the predominant isolates belonged to Legionella pneumophila serogroup 6 and to L. londiniensis.

During the study, no clinical cases of Legionnaires' disease were observed, and the antibody titres were generally low in the groups studied. However, the antibody titres of the patients increased slightly during their stay at the spa, approaching the values for the therapists. Mean antibody titres in the groups related with the spa were significantly higher than those in the blood donors against five of the seven legionella antigens tested. The largest number of elevated antibody titres in the exposed groups were to the L. pneumophila sg 5 and sg 6 antigens.

(Accepted February 15 1995)


c1 Author for correspondence: M. S. da Costa, Departamento de Bioquímica, Apartado 3126, Universidade de Coimbra, 3000 Coimbra, Portugal.