Abstract
Chlamydia psittaci is one of the primary pathogens responsible for community-acquired atypical pneumonia. If not treated promptly, it can progress to severe pneumonia and may lead to multiple organ dysfunction as well as secondary infections with multi-drug-resistant (MDR) bacteria. Omadacycline, a novel aminomethylcycline antibiotic derived from tetracycline, exhibits high activity against various bacterial strains. This case report describes a patient who developed severe pneumonia caused by Chlamydia psittaci in conjunction with a MDR bacterial infection. Despite initial treatment with moxifloxacin and doxycycline, the patient experienced treatment failure. The patient's condition deteriorated, presenting complications such as progressive infection, leukopenia, liver dysfunction, electrolyte imbalances, and respiratory alkalosis. Following the adjustment to omadacycline therapy for 48 hours, all complications were rapidly alleviated, leading to successful treatment of the patient.