We tested serum specimens from three groups of patients with pneumonia by i
ndirect immunofluorescence against Legionella-like amoebal pathogens (LLAPs
) 1-7, 9, 10, 12, 13; Parachlamydia acanthamoeba strains BN 9 and Hall's co
ccus; and Afipia felis. We found that LLAPs play a role (albeit an infreque
nt one) in community-acquired pneumonia, usually as a co-pathogen but somet
imes as the sole identified pathogen.