Legionella-Like and Other Amoebal Pathogens as Agents of Community-Acquired Pneumonia

Abstract and Introduction

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

A number of bacteria that grow only within amoebae and are closely related phylogenetically to Legionella species, Legionella-like amoebal pathogens (LLAPs), have been identified and characterized^[1]. The role of these bacteria as human pathogens is still largely unknown. Other microorganisms, e.g., Parachlamydia acanthamoeba strains BN 9^[2] and Hall's coccus^[3], also grow within amoebae. Afipia felis (once thought to be the etiologic agent of cat-scratch disease), a gram-negative rod, is difficult to grow on artificial medium but grows well in human monocytes and HeLa cells^[4]; this organism was recently reported to be an environmental bacterium probably associated with free-living amoebae and living in water^[5]. We tested serum specimens from three groups of patients with pneumonia to determine if any of these microorganisms cause disease.

Emerging Infectious Diseases. 2001;7(6) © 2001 Centers for Disease Control and Prevention (CDC)