To analyze the potential clinical risk factors and imaging characteristics of severe Chlamydia psittaci pneumonia.

A retrospective analysis was conducted on the clinical data of 54 patients with Chlamydia psittaci pneumonia admitted to the First Affiliated Hospital of Anhui Medical University from June 2020 to May 2025. All patients were diagnosed via metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid. Patients meeting the inclusion criteria were divided into a severe group (requiring intensive care unit treatment) and a non-severe group. Clinical data were compared between the two groups. Multivariate logistic regression was used to identify risk factors associated with severe Chlamydia psittaci pneumonia.

The duration of fever after admission was significantly longer in the severe group compared to the non-severe group (P<0.05). The severe group had a higher prevalence of wheezing as a chief complaint and chills as an initial symptom (P<0.05). Compared to the non-severe group, the severe group had significantly lower levels of lymphocytes, partial pressure of oxygen, monocytes, albumin, and platelets (P<0.05). Conversely, the severe group exhibited significantly higher levels of white blood cells, neutrophils, neutrophil-to-lymphocyte ratio, lactate dehydrogenase, aspartate aminotransferase, direct bilirubin, indirect bilirubin, brain natriuretic peptide, procalcitonin, prothrombin time, fibrin degradation products, D-dimer, and a longer recovery time for C-reactive protein (CRP) (P<0.05). CT imaging revealed that the severe group had significantly more consolidations, air bronchograms, pleural effusions, and multilobar lesions compared to the non-severe group (P<0.05). During treatment, the severe group required respiratory support at a higher rate (P<0.05). Multivariate logistic regression analysis identified the following independent risk factors for severe Chlamydia psittaci pneumonia: duration of fever after admission (OR=1.460, 95%CI: 1.151~1.852, P<0.05), chills as an initial symptom (OR=5.473, 95%CI: 1.401~21.109, P<0.05), neutrophil count ≥9.5×10⁹/L (OR=10.500, 95%CI: 2.555~43.143, P<0.05), white blood cell count ≤1.1×10⁹/L (OR=4.952, 95%CI: 1.489~16.466, P<0.05), direct bilirubin ≥19 μmol/L (OR=4.667, 95%CI: 1.410~15.448, P<0.05), lactate dehydrogenase ≥100 U/L (OR=7.286, 95%CI: 1.775~29.907, P<0.05), procalcitonin ≥13 ng/ml (OR=4.062, 95%CI: 1.115~6.131, P<0.05), prothrombin time ≥4 s (OR=4.250, 95%CI: 1.169~15.454, P<0.05), air bronchogram on CT imaging (OR=6.538, 95%CI: 1.793~23.843, P<0.05), and pleural effusion (OR=2.854, 95%CI: 1.329~21.109, P<0.05).

The clinical manifestations of Chlamydia psittaci pneumonia are atypical. Early bronchoscopy with mNGS of bronchoalveolar lavage fluid can aid in early diagnosis. Specific clinical indicators, laboratory parameters, and CT imaging features serve as independent risk factors for severe Chlamydia psittaci pneumonia.