Detection of Legionella pneumophila Antigen in Urine Samples: Recognition of Serogroups and Monoclonal Subgroups

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Abstract
A study by Benson et al. compared the usefulness of urinary antigen detection for diagnosing Legionnaires’ disease caused by L. pneumophila serogroup 1 of different monoclonal subgroups in addition to cases caused by other serogroups. A total of 152 urine samples from 152 patients with culture-proven legionellosis were tested. Urine samples were tested simultaneously using Binax Legionella urinary enzyme immunoassay (EIA) and Biotest Legionella Urin Antigen enzyme immunoassay (EIA). Taking all cases of legionellosis into account, a sensitivity of 77% for both Binax EIA and Biotest EIA was found. This is in good agreement with other studies. In addition, the authors demonstrated that the sensitivities for infections caused by monoclonal antibody (MAb) 3/1- and MAb 2-positive strains are much higher, exceeding 95%; thus, urinary antigen detection is the best method for diagnosing community-acquired as well as travel-associated cases. Diagnosis of such infections has especially far-reaching implications for nosocomially acquired legionellosis, which is significantly more often caused by strains belonging to monoclonal subgroups OLDA/Oxford and Bellingham or to serogroups 2 to 15 than are community-acquired infections.