PURPOSE: The purpose of this study was to compare the clinical and thin-section CT findings in patients with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA).
METHODS: We retrospectively identified 201 patients with acute MRSA pneumonia and 164 patients with acute MSSA pneumonia who underwent chest thin-section CT examinations between January 2004 and March 2009. Patients with concurrent infectious disease were excluded from our study. Consequently, our study group comprised 68 patients with MRSA pneumonia (37 male, 31 female) and 83 patients with MSSA pneumonia (32 male, 51 female). Clinical findings in the patients were assessed. Parenchymal abnormalities, lymph node enlargement, and pleural effusion were assessed.
RESULTS: Underlying diseases such as cardiovascular were significantly more frequent in the patients with MRSA pneumonia than in those with MSSA pneumonia. CT findings of centrilobular nodules, especially with a tree-in-bud pattern, and bronchial wall thickening were significantly more frequent in the patients with MSSA pneumonia than those with MRSA pneumonia (p=0.038, p=0.007, and p=0.039, respectively). In the group with MRSA, parenchymal abnormalities were observed to be mainly peripherally distributed and the frequency was significantly higher than in the MSSA group (p=0.028). Pleural effusion was significantly more frequent in the patients with MRSA pneumonia than those with MSSA pneumonia (p=0.002).
CONCLUSIONS: Findings from the evaluation of thin-section CT manifestations of pneumonia with clinical manifestations may be useful to distinguish between patients with acute MRSA pneumonia and those with MSSA pneumonia.
CLINICAL IMPLICATIONS: Unlike MSSA, effective antibodies for treating MRSA are usually not part of initial empiric antibiotic regimens for community-acquired pneumonia. Therefore, the early recognition of MRSA pneumonia and initiation of appropriate antibiotics are important to reduce morbidity and mortality.
DISCLOSURE: The following authors have nothing to disclose: Fumito Okada, Yumiko Ando, Keiko Morikawa, Asami Ono, Tomoko Nakayama, Hiromu Mori
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