title: Immunologic diagnosis of Legionnaires' disease: cross-reactions with anaerobic and microaerophilic organisms and infections caused by them.
abstract: The hundred twenty-four isolates of anaerobic and microaerophilis organisms were examined with a polyvalent direct immunofluorescent antibody (DFA) reagent directed against Legionella pneumophila, serogroups (SG) I-IV. Three of 53 isolates of Bacteroides fragilis cross-reated with the SG I component of the reagent. Rabbit antisera to three SG I strains of L. pneumophila cross-reacted with these three B. fragilis isolates, and cross-reactivity was not due to preexisting rabbit antibodies; antisera to a fourth SG I strain did not cross-react with these isolates. Indirect fluorescent antibody (IFA) examinations of convalescent-phase sera from eight of 41 patients with B. fragilis group infections showed titers of greater than or equal to 1:128 or a fourfold or greater seroconversion against L. pneumophila, SG I. All eight patients had bacteremia due to B. fragilis, but five B. fragilis isolates available from these patients were DFA-negative. Thus, false-positive reactions may result from DFA as well as IFA examinations of sera from patients with B. fragilis infections.
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D000907:Antibodies, Bacterial; D000918:Antibody Specificity; D001442:Bacteroides Infections / Q000175:diagnosis; D001441:Bacteroides fragilis / Q000276:immunology; D003429:Cross Reactions; D005189:False Positive Reactions; D005455:Fluorescent Antibody Technique; D006801:Humans; D007877:Legionnaires' Disease / Q000175:diagnosis*; D011817:Rabbits
chemical_list: D000907:Antibodies, Bacterial