The occurrence of antibodies against Legionella pneumophila in patients with autoimmune rheumatic diseases

INTRODUCTION Patients with autoimmune rheumatic diseases are more susceptible to infection, owing

to the underlying disease itself or to its treatment. Most commonly, infections affect the respiratory and

urinary tracts. One of the etiological factors of infections in these patients is the bacteria of the genus

Legionella.

OBJECTIVES The aim of the study was to assess the prevalence of anti-Legionella pneumophila

(L. pneumophila) antibodies in patients with autoimmune rheumatic diseases and to analyze individual and

environmental risk factors for the development of Legionella infection in patients with positive antibody results.

PATIENTS AND METHODS The study group consisted of 165 patients with autoimmune rheumatic diseases

and 100 healthy subjects. Serum samples were tested for the presence of specific antibodies in

the immunoglobulin (Ig) M and IgG classes against L. pneumophila serogroups 1 to 7 (SG 1–7) and the

IgG class for serogroup 1 (SG 1).

RESULTS Antibodies against L. pneumophila were found in 7 patients (4%): 5 cases with antibody positivity

only in the IgG class and 2 cases with antibody positivity in both classes. In patients with positive

IgG antibodies for SG 1–7, specific antibodies for L. pneumophila SG 1 were not detected. In the control

group, positive results were obtained in 9 cases (9%): IgM positivity in 6 (6%) and IgG positivity in 3 (3%).

CONCLUSIONS The frequency of antibodies to L. pneumophila in our patients is comparable to that in

healthy individuals. L. pneumophila should be recognized as a potential pathogen in patients with autoimmune

rheumatic diseases. Primary disease condition, immunosuppressive therapy, and other risk

factors should not be ignored in these patients.

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