Legionella pneumophila: laboratory diagnosis in developing countries like Pakistan.

Three hundred random sputum samples were collected for analysis from cases of mild to severe respiratory infections and screened for Legionella pneumophila by both the culture method and also the direct fluorescent antigen test. In one third of the cases, blood specimen was also collected and screened for Legionella serum antibodies. With the direct fluorescent test it was possible to identify Legionella in 9% of the samples while the culture gave positive results in 4.3% of cases. Diagnostic antibody titers (1:256) were obtained in 12% of the samples while another 12% cases showed serum antibody titers of 1:64 to 1:128. In Pakistan where antibiotics are used extensively, the direct fluorescent examination of sputum samples gives more accurate diagnosis of Legionella cases than the culture method.