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

Abstract

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.

Occurrence of culturableLegionella pneumophilain drinking water distribution systems

“…The true positivity rate in this study (rounds 1 and 2) was lower than the Legiolert specificity reported by Sartory et al (), where 14 of 290 premise water samples (4.8%) did not serotype as a L. pneumophila strain, or by Spies et al (), who reported that the Legiolert method had a specificity for L. pneumophila of 97.9% (2.1% nonconfirming) for premise samples, both of which are comparable to the 95.3% specificity for the ISO 11731 method. Legiolert nonpotable evaluations have primarily been conducted with cooling towers, for which the true positivity rate was reported to be 95.1% (Rech et al, ). The differences observed in this study for both the potable and nonpotable evaluations compared with other published results are likely derived from both the novel sample types evaluated and the paucity of overall positive samples.…”

“…Recently, IDEXX Laboratories Inc. (Westbrook, ME) developed a culture‐based assay for the enumeration of L. pneumophila that is easy to use by water utilities (LeChevallier, ). The test has been shown by several researchers to result in equivalent or higher counts of L. pneumophila from potable, nonpotable, and water cooling tower samples (Petrisek & Hall, ; Rech, Swalla, & Dobranic, ; Sartory, Spies, Lange, Schneider, & Langer, ; Spies et al, ).…”

Legionella pneumophila occurrence in drinking water supplied by private wells

“…IDEXX Legiolert is a relatively newly developed culture method used for the detection of L. pneumophila and, when comparing sensitivity of confirmed positive samples in prior studies to conventional culture methods, Legiolert tended to yield better sensitivity in in potable water samples (Sartory et al 2017). Legiolert similarly exhibited higher sensitivity in potable water samples (Petrisek and Hall 2018) and equivalent sensitivity in non-potable water samples compared to plate culture methods (Petrisek and Hall 2018;Rech et al 2018). While the results herein were unexpected, the number of overall positive comparative data points was small and, as such, an expanded sample size would be more informative for comparative performance with matrices like well water, which have not been previously validated with Legiolert.…”

Monitoring distribution systems for Legionella pneumophila using Legiolert

“…Similarly, for the nonpotable water analysis, Legiolert had a false positivity value of <0.9% and a specificity of 100%. Similarly, Rech, Swalla, and Dobranic () reported increased sensitivity, low false positive rates, and less interference for nonpotable water cooling tower samples than the Centers for Disease Control and Prevention (CDC) culture method.…”