INTRODUCTION: Serious respiratory infections can occur in both in-hospital and out-of-hospital settings. These infections are known as community-acquired pneumonias (CAPs). Streptococcus pneumoniae and other microorganisms commonly cause atypical pneumonia. This study examined the clinical features, medication therapy, and prognosis of 85 cases of community-acquired pneumonia (CAP) caused by Mycoplasma pneumoniae (MPP) and Chlamydia psittaci(C. psittaci)neumoniae (CPP). METHODS: A retrospective analysis was conducted at Shaoxing People's Hospital from July 2021 to August 2024, using targeted next-generation sequencing (tNGS) of bronchoalveolar lavage fluid (BALF). Patients were classified into the MPP group (54 patients) and the CPP group (31 patients). Compared with the control group, the CPP group had a significantly lower proportion of patients with a contact history of poultry and birds, a shorter length of hospital stay, and a lower percentage of severe pneumonia cases. RESULTS: The MPP group demonstrated higher incidences of cough and sputum production
conversely, the occurrences of fever, fatigue, diminished appetite, and generalised myalgia were comparatively lower. The MPP group exhibited markedly diminished levels of neutrophils, C-reactive protein, procalcitonin, erythrocyte sedimentation rate, heparin-binding protein, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, direct bilirubin, pH, lactic acid, and D-dimer compared with the CPP group. In contrast, the MPP group had a markedly higher lymphocyte count, platelet count, albumin levels, as well as higher concentrations of blood sodium and blood chloride. The drug treatment regimens differed between the two groups, resulting in one unfavourable outcome within the MPP group. CONCLUSION: In summary, fatigue, fever, and reduced appetite are more prominent symptoms in patients with CPP, whereas cough and sputum production are the primary manifestations of MPP. Pleural effusion is more prevalent in patients with CPP, Additionally, these patients also have increased inflammatory responses and decreased immune function.