Community-Acquired Chlamydia psittaci Severe Pneumonia: A Case Report

Abstract

Chlamydia psittaci, the causative agent of psittacosis, is an intracellular bacterium typically transmitted from birds to humans, leading to atypical pneumonia. We present a case of a 60-year-old man with no reported bird exposure but a history of working as a chief cook, potentially exposed to poultry. He presented with high fever, diffuse soreness, and left-sided pulmonary consolidation. Initial treatment with β-lactams was ineffective, but a multiplex PCR on bronchoalveolar lavage identified C. psittaci DNA. Therapy was switched to moxifloxacin, resulting in rapid clinical improvement. C. psittaci causes approximately 1% of community-acquired pneumonias, often underdiagnosed due to nonspecific symptoms and the need for advanced diagnostic tools like nucleic acid amplification tests (NAATs) or metagenomic next-generation sequencing (mNGS). The bacterium is endemic in birds and poultry, with human infections linked to occupational exposure or contact with infected animals. Diagnosis relies on NAAT and mNGS, as serology and culture are less practical. Treatment with tetracyclines, quinolones, or macrolides is effective, reducing mortality from 10%-20% to < 1%. Preventive measures, including protective equipment for high-risk individuals and treatment of infected birds, are crucial. Mandatory reporting of cases could improve understanding of the disease burden. This case highlights the importance of considering psittacosis in atypical pneumonia, even without direct bird exposure, and the role of NAAT or mNGS in accurate diagnosis.

Keywords: Chlamydia psittaci; atypical pneumonia; community-acquired pneumonia; multiplex PCR respiratory panel; zoonosis.

Figure 1

Chest CT scan showing subpleural lobar condensation in the left upper lobe with air bronchogram.

Figure 2

Two months later, chest CT scan showing complete resolution of infiltrate from posterior pneumonia of the upper left lobe.