Intratracheal infection with L. pneumophila subtypes.

Two strains of Legionella pneumophila serogroup 1 (UH1 and RH1) were injected intratracheally into guinea pigs. There were no differences in infectivity or mortality, but there was evidence of disseminated infections in more guinea pigs infected with the UH1 strain. Guinea pigs that received sublethal inocula were then rechallenged intratracheally and had a lower mortality rate than did previously uninfected controls.