Chapter 110 : Field Evaluation of the Binax Equate Test Kit for Enumeration of Legionella pneumophila Serogroup 1 in Cooling Water Samples

Abstract:

This chapter investigates on the efficacy of detection of Legionella pneumophila serogroup 1 (sg 1) in cooling waters using the Binax Equate Legionella water test. The test kit offers a rapid detection method (45 min) for L. pneumophila sg 1 in environmental water samples. A high proportion of Binax positive results were also between 1.0 and 1.9 OD450. Legionella species were cultured from 22% (n = 31) of all cooling water samples. Presumptive Pseudomonas spp. were isolated from 42.9% of all cooling water samples. Two samples grew to confluence, indicating very high concentrations of Pseudomonas spp. in those samples. Presumptive P. fluorescens was isolated from 21.9% of all cooling water samples. The post-treatment results for the heat-treated sample showed that the average absorbance decreased following the treatment. A large number of false-positive Binax results were recorded whether or not Legionella spp. were cultured from the sample. Alternatively, the test also recognized heat-killed cells and false-positive results may have been due to the presence of dead L. pneumophila in the cooling systems. The results suggest that this system lacks the required specificity for routine use in cooling towers or other water systems. It seems likely that the test method would produce false-positive results in systems where disinfection was applied. False-positive results from cooling tower samples in this study may have been due to the presence of killed L. pneumophila sg 1. The results point to the necessity of indication of viability in future environmental tests for Legionella.