Deja Vu All Over Again: Rapid Enumeration of Legionella pneumophila in Water

Abstract

Delgado-Viscogliosi and colleagues recently reported a rapid method for detecting viable Legionella pneumophila in water using immunofluorescence microscopy (1). Carl Fliermans and colleagues reported a similar assay in this journal 24 years ago (3) and later reported an assay for viability using a tetrazolium dye (4). Both the papers published in the 1980s and the recently published paper reported that the immunofluorescence microscopy method detected greater numbers of bacterial cells than did culture, and both argued that the greater sensitivity of the microscopic method was probably due to poor culture recovery of the Legionella bacteria. Another possibility for this poor correlation is nonspecificity of the antibodies used. A number of clinical and environmental bacteria, many of which are deposited at the ATCC, cross-react with L. pneumophila polyvalent antibodies (2). The immunofluorescence microscopy enumeration method was in vogue for a number of years in the 1980s but fell out of favor due to the poor correlation between viable counts and the microscopic method. It is not clear to me that adding an assay for viability will improve the utility of this assay method, but knowing that the antibodies used do not cross-react with known cross-reacting strains would be useful information. It would be of importance for Delgado-Viscogliosi and colleagues to test their antibodies against the known cross-reacting bacteria deposited at ATCC, as well as to acknowledge the seminal work on this method by Fliermans and colleagues.