Comparison of cross-staining reactions by Pseudomonas spp. and fluorescein-labeled polyclonal and monoclonal antibodies directed against Legionella pneumophila

Abstract

Commercially prepared polyclonal antisera to Legionella pneumophila are known to cross-react with organisms of the genus Pseudomonas. To determine whether a commercially available monoclonal antibody reagent specific for L. pneumophila would also cross-react with pseudomonads, a two-laboratory study was undertaken to test both monoclonal and polyclonal reagents against 33 isolates of Pseudomonas spp., including 25 Pseudomonas aeruginosa , 4 P. putida, 2 P, maltophilia, 1 P. fluorescens, and 1 P. alcaligenes. Four antisera were tested; polyclonal anti-legionella antisera pools A and B (Centers for Disease Control [CDC] Atlanta, Ga.), polyclonal 1-6 antisera (BioDx, Inc., Denville, N.J.), and a monoclonal antibody reagent produced by Genetic Systems Corp., Seattle, Wash. All reagents were labeled with fluorescein. Cross-staining reactions were found with the BioDx L. pneumophila antisera and 10 isolates of Pseudomonas. Four of these isolates demonstrated cross-staining with CDC pool A. When tested with individual serotype-specific reagents (CDC), three of four cross-reacted with L. pneumophila serotype 1 antisera; the fourth cross-reacted with serotype 3. No cross-staining reactions were noted with the monoclonal reagent and any of the pseudomonas tested, demonstrating that the Genetic Systems Corp. monoclonal is the most specific of the four reagents tested.