title: Evaluation of pulmonary dysfunctions and acid-base imbalances induced by Chlamydia psittaci in a bovine model of respiratory infection.
abstract: BACKGROUND
  Chlamydia psittaci (Cp) is a respiratory pathogen capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection. To elucidate the pathogenesis of this infection, a translational large animal model was recently introduced by our group. This study aims at quantifying and differentiating pulmonary dysfunction and acid-base imbalances induced by Cp.
  
  
  METHODS
  Forty-two calves were grouped in (i) animals inoculated with Cp (n = 21) and (ii) controls sham-inoculated with uninfected cell culture (n = 21). For pulmonary function testing, impulse oscillometry, capnography, and FRC (functional residual capacity) measurement were applied to spontaneously breathing animals. Variables of acid-base status were assessed in venous blood using both (i) traditional Henderson-Hasselbalch and (ii) strong ion approach.
  
  
  RESULTS
  Both obstructive and restrictive pulmonary disorders were induced in calves experimentally inoculated with Cp. Although disorders in respiratory mechanics lasted for 8-11 days, the pattern of spontaneous breathing was mainly altered in the period of acute illness (until 4 days post inoculation, dpi). Expiration was more impaired than inspiration, resulting in elevated FRC. Ventilation was characterised by a reduction in tidal volume (-25%) combined with an increased percentage of dead space volume and a significant reduction of alveolar volume by 10%. Minute ventilation increased significantly (+50%) due to a compensatory doubling of respiratory rate. Hyperventilatory hypocapnia at 2-3 dpi resulted in slightly increased blood pH at 2 dpi. However, the acid-base equilibrium was additionally influenced by metabolic components, i.e. the systemic inflammatory response, all of which were detected with help of the strong ion theory. Decreased concentrations of albumin (2-10 dpi), a negative acute-phase marker, resulted in a decrease in the sum of non-volatile weak acids (Atot), revealing an alkalotic effect. This was counterbalanced by acidic effects of decreased strong ion difference (SID), mediated by the interplay between hypochloraemia (alkalotic effect) and hyponatraemia (acidic effect).
  
  
  CONCLUSIONS
  This bovine model was found to be suitable for studying pathophysiology of respiratory Cp infection and may help elucidating functional host-pathogen interactions in the mammalian lung.
authors: Institute of Molecular Pathogenesis at 'Friedrich-Loeffler-Institut' (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany.
authors: Carola
authors: C
authors: Ostermann
authors: Institute of Molecular Pathogenesis at 'Friedrich-Loeffler-Institut' (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany.
authors: Susanna
authors: S
authors: Linde
authors: Freie Universität Berlin, Faculty of Veterinary Medicine, Oertzenweg 19b, 14163 Berlin, Germany.
authors: Christiane
authors: C
authors: Siegling-Vlitakis
authors: Institute of Molecular Pathogenesis at 'Friedrich-Loeffler-Institut' (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany.
authors: Petra
authors: P
authors: Reinhold
keywords: Acid–base status; Animal model; Chlamydia psittaci; Pulmonary function