[Clinical characteristics analysis of patients with pneumonia infected by Chlamydia psittaci]

To explore the clinical characteristics of pneumonia infected by Chlamydophila psittaci (C. psittaci).

A retrospective analysis was performed on 3 cases of C. psittaci pneumonia admitted to People's Hospital of Tongling City from July 2019 to January 2020. The patients' contact history, clinical manifestations, laboratory examination, imaging characteristics and evolution, etiology, treatment process and outcome were analyzed, so as to provide experience for the diagnosis and prevention of C. psittaci pneumonia.

The 3 patients had been infected through pet or zoonotic exposures. All symptoms included high fever (body temperature > 39 centigrade), cough, sputum, chest tightness and dyspnea. The disease progressed rapidly, with severe acute respiratory distress syndrome (ARDS) and shock as the main manifestations, but the damages to the heart, liver and kidney were mild. Laboratory tests showed that C-reactive protein (CRP, all > 200 mg/L) and neutrophil proportion (Neut%, > 0.90) were significantly increased, while white blood cell count (WBC) and procalcitonin (PCT) were not significantly increased. Chest computed tomography (CT) showed inflammatory infiltration with interstitial changes, either unilateral or bilateral. Chest X-ray showed large areas of inflammatory infiltrations, fan-shaped or wedge-shaped to the edge of pleura. After 7 days of treatment, the bedside computed X-ray (CR) showed absorption of infiltration. After 11-13 days, the CT reexamination indicated lung infection was basically absorbed. Metagenomic next-generation sequencing (mNGS) confirmed the presence of C. psittaci in patients' sputum. It was sensitive to quinolones and tetracyclines. The patients' body temperature dropped to normal after 2-3 days of antibiotics, and all patients were extubated and transferred to normal ward 10 days later. The total course of illness was 20-30 days.

The patients with C. psittaci pneumonia are critically ill, and clinical manifestations of moderate to severe ARDS and shock are common. Early diagnosis depends on mNGS, and reasonable treatment is important for prognosis.