Alterations in respiratory mechanics and pulmonary ventilation induced by Chlamydia psittaci
Chlamydia psittaci (Cp) is capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection occurring in patients with pulmonary emphysema and/or COPD. To elucidate the pathogenesis of this infection, a defined respiratory model in calves was recently introduced , which resembles the situation in humans more closely than mice. This investigation was undertaken to identify pulmonary dysfunctions induced by Cp. Eighteen calves were inoculated with Cp, whereas another 18 control calves received uninfected cell culture. Respiratory disorders were characterized non-invasively applying pulmonary function tests from human medicine (i.e. impulse oscillometry and capnography) to spontaneously breathing animals from 7 days before challenge until 14 days post inoculation. Compared to control calves, calves exposed to Cp had significantly increased respiratory resistance at low frequencies (≤ 5 Hz), while respiratory reactance at all frequencies (3 – 15 Hz) decreased significantly, indicating that both obstructive and restrictive pulmonary disorders were induced by the pathogen. In spontaneous breathing, expiration was more impaired than inspiration. Alveolar hypoventilation was confirmed by decreased tidal volume, increased dead space ventilation, increased FRC, and decreased end-tidal CO2. In conclusion, this bovine model has been found to be suitable for studying functional host-pathogen interactions in the mammalian lung. Pulmonary dysfunctions assessed in this model provide relevant insights into the pathophysiology of acute respiratory illness induced by Cp.