Development and evaluation of diagnostic radiometric assays for serogroup 4 L. pneumophila urinary antigens

We previously reported that 80% of patients with serogroup 1 Legionella pneumophila pneumonia excrete detectable quantities of specific antigens in their urine. The purpose of this study was to determine whether specific antigens can be detected in urine from patients with serogroup 4 L. pneumophila pneumonia. Antisera were prepared in 15 rabbits and used to set up 25 solid-phase radioimmunoassays. The best of these assays detected specific antigens in urine from 4 of 5 patients with culture-proven serogroup 4 infections and from 1 of 2 patients with culture-proven serogroup 10 infections. None of 100 control specimens was positive in the assays. The antigens from serogroup 4 and 10 infections behaved differently in the assays, suggesting that they are not identical molecules. This study demonstrates that it is possible to detect specific antigens in the urine of patients with serogroup 4 L. pneumophila pneumonia. This may be a useful method for diagnosing these infections rapidly.