Evaluation of Legiolert for Quantification of Legionella pneumophila from Non-potable Water

Legiolert® is a new culture method for quantification of Legionella pneumophila, which is the primary species associated with Legionnaires’ disease. The test is based on a most probable number approach, and differs significantly from traditional culture methods by providing results at 7 days, rapid sample preparation and analysis, and objective interpretation of test results. In this study, we compared the performance of Legiolert with the U.S. Centers for Disease Control and Prevention (CDC) method for detection of L. pneumophila from non-potable samples, primarily comprising cooling tower waters. Our results demonstrated no significant difference between Legiolert and the CDC method for quantification of L. pneumophila. However, Legiolert showed a significant increase in sensitivity when water samples containing higher L. pneumophila concentrations were examined. Cooling tower waters often contain non-Legionella organisms (NLO) that interfere with traditional Legionella test methods, and we observed varying degrees of NLO interference on many CDC method plates. In contrast, Legiolert was resistant to NLO interference and produced a very low rate of false-positive results. Collectively, Legiolert is a sensitive and specific method for quantification of L. pneumophila from non-potable water that provides advantages over the CDC method.