Abstract
BACKGROUND: Chlamydia abortus is a zoonotic pathogen that causes miscarriage, stillbirth, and sepsis of pregnancy in pregnant women when it infects humans. However, it rarely causes pneumonia in humans. CASE PRESENTATION: This case reports a case of severe pneumonia characterized by high fever and cough, and the disease rapidly progressed to dyspnea. The patient was treated with moxifloxacin and doxycycline. Chlamydia abortus was detected in bronchoscopy examination and bronchoalveolar lavage fluid (BALF) through metagenomic next-generation sequencing (mNGS)-DNA. A weak positive for influenza A (H1N1) antigen was also found in the throat swab tested. Subsequently, we added mabaloxavir and replaced doxycycline with an intravenous infusion of omadacycline. After effective treatment, the patient developed a urinary tract infection, and the treatment plan was adjusted to meropenem combined with omadacycline. The patient's condition improved, and she was discharged on the 14th day of admission. CONCLUSION: This is the first report of cases of non-pregnant female patients with Chlamydia abortus infection pneumonia. Consequently, infections with Chlamydia abortus can result in severe respiratory distress, disturbance of water and electrolyte balance, and abnormal liver function, which requires timely diagnosis and correct use of antibiotics by clinicians. Consequently, the mixed infection of H1N1 and Chlamydia abortus aggravated the complexity of the condition and treatment. Combining tetracycline and quinolone is effective for treating severe pneumonia with Chlamydia abortus infection.