Validation of the Legipid bioalarm Legionella assay

Legipid Bioalarm Legionella is a test based on combined magnetic immunocapture and enzyme-immunoassay (CEIA) for the detection of Legionella pneumophila in water. Anti-L. pneumophila antibodies are immobilized on magnetic microspheres. Immunomagnetic analysis is applied to preconcentrated water samples in a final test volume of 9 mL. The method was compared with the standard culture method on both spiked and naturally contaminated water samples. The test was evaluated in potable, industrial, and natural water matrixes, according to the scope of the ISO 11731 reference method. These waters were tested with the target at levels ranging from low (10-99 CFU/mL) to high (100-999 CFU/mL); a Chi-square value of 1.8 indicated that there was no significant difference between the test and the reference method. The false-positive rate was 7%, and the false-negative rate 2%. For the inclusivity study, all 17 strains of L. pneumophila of different serogroups reacted with the test. For the exclusivity study, 17 strains of other Legionella species and 16 non-Legionella strains were tested. There were no cross-reactions with non-Legionella strains. L. beliardensis, L. adelaidensis, and one environmentally isolated Legionella sp. produced a positive result at high concentrations of 1800, 230, and 3900 CFU/mL, respectively. Agreement between the two methods was 95.9%.