Determination of antigenic relationships among legionellae and non-legionellae by direct fluorescent-antibody and immunodiffusion tests

Abstract

Water isolates (5) and a human tracheal isolate taken at autopsy reacted strongly with working dilutions of Legionella fluorescent-antibody conjugates. Two isolates of Pseudomonas fluorescens (EB and CDC93), 1 isolate of the Flavobacterium-Xanthomonas group (CDC65) and 1 isolate of P. alcaligenes (CDC11) reacted with L. pneumophila serogroup 1 conjugate. P. alcaligenes ABB 50 reacted with a L. pneumophila serogroup 3 conjugate; P. maltophilia reacted with the L. micdadei conjugate. Antisera and labeled conjugates were prepared for these new cross-reacting isolates; their relationships to the legionellae were examined by direct fluorescent-antibody and immunodiffusion tests. A nonreciprocal cross-reaction existed between L. micdadei and P. maltophilia and between serogroup 3 of L. pneumophila and P. alcaligenes ABB50. Of the 4 isolates that reacted with serogroup 1 of L. pneumophila, P. fluorescens CDC93 had the strongest relationship; the others had only minor relationships. Although cross-reactivity among non-legionellae and legionellae has not been a major problem, these findings are relevant to the interpretation of direct fluorescent-antibody tests for detecting these bacteria.