Serological differences in Legionella pneumophila infections

Guinea pigs were infected with two subtypes of Legionella pneumophila serogroup 1 (UH1 and RH1). Seroconversion by indirect fluorescent-antibody assay was demonstrated in 94 to 97% of guinea pigs when the challenge strain was used as the antigen. The standard Philadelphia 1 antigen demonstrated seroconversion in 94% UH1-challenged animals, but in only 66% of RH1-challenged animals.