Evaluation of a Legionella urinary antigen enzyme immunoassay for rapid detection of Legionella pneumophila in water samples

Despite advances in medium formulations and pretreatment techniques, recovery of Legionella from water samples can still be quite low, difficult and time consuming. The aim of this study was to evaluate the utility of a Legionella urinary antigen enzyme immunoassay (Bartels ELISA, Trinity Biotech, Ireland) for the detection of Legionella in water samples. Reference ATCC Legionella strains were used to spike water samples to a final concentration of 104–105 cfu/ml. The lower detection limit of the test for all Legionella pneumophila serogroups was assessed by serial dilutions of spiked water samples. Legionella antigen was detected in all filtered samples except for those spiked with L. bozemanii and L. longbeachae. The lower detection limit for soluble L. pneumophila serogroup 1 antigen was 780 cfu/ml. Bartels ELISA could be a useful method for antigen detection in water samples when a high recovery of L. pneumophila is suspected. The test could be used as a rapid screening method for the detection of Legionella in a large number of samples. However, the low sensitivity of the test requires to keep on performing conventional culture for isolation and for further studies on isolated bacteria.