PT - JOURNAL ARTICLE AU - Markus Lohr AU - Annette Prohl AU - Carola Ostermann AU - Wieland Schroedl AU - Elisabeth Liebler-Tenorio AU - Gilbert Greub AU - Petra Reinhold TI - <em>Parachlamydia acanthamoebae</em> as a respiratory pathogen: Challenge dose titration in a bovine model DP - 2014 Sep 01 TA - European Respiratory Journal PG - P2539 VI - 44 IP - Suppl 58 4099 - http://erj.ersjournals.com/content/44/Suppl_58/P2539.short 4100 - http://erj.ersjournals.com/content/44/Suppl_58/P2539.full SO - Eur Respir J2014 Sep 01; 44 AB - Background: The majority of community acquired pneumonia (CAP) in humans fails to be diagnosed aetiologically. Besides Chlamydia spp., Chlamydia-like organisms are thought to be causative in CAP. Pneumopathogenic potential has been described for Parachlamydia (P.) acanthamoebae, a well studied agent among the Chlamydia-like organisms.Objective: This study aimed to evaluate the pathogenicity of Parachlamydia (P.) acanthamoebae as a potential agent of lower respiratory tract disease. A bovine model of induced lung infection was introduced for translational reasons.Method: Intrabronchial inoculation with P. acanthamoebae was performed in healthy calves aged 2-3 months (n=30) using two different challenge doses: 108 and 1010 inclusion-forming units (ifu) per animal. Controls received heat inactivated pathogen.Results: While the challenge with 108 ifu of viable Parachlamydia resulted in a mild degree of clinical illness, the dose of 1010 ifu induced a respiratory desease that became clinically apparent 1-2 days after challenge. Parachlamydiae were detected in neutrophils and alveolar macrophages within pulmonary lesions by immunohistochemistry. This was in accordance with molecularbiological findings as well as with re-isolation of Parachlamydia. Clinical outcome, acute phase reactants, pathological findings and antigen load exhibited an initial dose-dependent effect of severity.Conclusion: The bovine lung was shown to be susceptible for P. acanthamoebae. Recommending the challenge dose of 1010 ifu, this large animal model is suitable to elucidate host-pathogen interactions.