[Clinical characteristics of a case of severe pneumonia caused by coinfection of COVID-19 and Chlamydia Psittaci].

A 69-year-old female patient was admitted to the Department of Respiratory and Critical Care Medicine, Affiliated Hospital of Xuzhou Medical University due to a "cough and fever for eight days". On admission, a coronavirus disease (COVID-19) nucleic acid test was positive, and a chest CT scan showed progressive patchy shadows and consolidation shadows in both lungs. Arterial blood gas analysis showed type Ⅰ respiratory failure. The primary diagnosis was severe community-acquired pneumonia in an older adult without underlying disease. However, oxygen inhalation, steroid, anti-inflammatory, and antibacterial empirical treatment with piperacillin/tazobactam was ineffective. Metagenomic next-generation sequencing of bronchoscopy alveolar lavage fluid showed Chlamydia psittaci(C. psittaci). Severe pneumonia was confirmed, caused by coinfection with severe acute respiratory syndrome coronavirus 2 and C. psittaci. A combination of doxycycline and moxifloxacin significantly improved the targeted and symptomatic treatment of the underlying cause. After discharge, the patient recovered within four weeks of follow-up. Therefore, clinicians should be alert to the possibility of coinfection of C. psittaci in patients already diagnosed with COVID-19.