REVIEW ARTICLE Amoebal pathogens as emerging causal agents of pneumonia Fred´ eric´ Lamoth1 & Gilbert Greub1,2 1Infectious Diseases Service, University of Lausanne, Lausanne, Switzerland; and 2Center for Research on Intracellular Bacteria, Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland Correspondence: Gilbert Greub, Center for Abstract Research on Intracellular Bacteria, Institute of Microbiology, University Hospital Center and Despite using modern microbiological diagnostic approaches, the aetiological University of Lausanne, Rue du Bugnon 46, agents of pneumonia remain unidentified in about 50% of cases. Some bacteria 1011 Lausanne, Switzerland. Tel.: 141 21 that grow poorly or not at all in axenic media used in routine clinical bacteriology 31449 79; fax: 141 21 31440 60; e-mail: laboratory but which can develop inside amoebae may be the agents of these lower
[email protected] respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae- resisting bacteria, which coevolved with amoebae to resist their microbicidal Received 24 September 2009; revised 30 machinery, may have developed virulence traits that help them survive within November 2009; accepted 2 December 2009. human macrophages, i.e. the first line of innate immune defence in the lung. We Final version published online 22 January 2010. review here the current evidence for the emerging pathogenic role of various DOI:10.1111/j.1574-6976.2009.00207.x amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Editor: Colin Berry Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.). Keywords free-living amoebae; amoebae-resisting bacteria; Legionella; Chlamydia-like bacteria; mycobacteria; pneumonia.