Clinical features of mixed infections in patients with Streptococcus pneumoniae pneumonia

: We retrospectively analyzed the severity, the mortality and the initial antimicrobial therapy in 195 patients with Streptococcus pneumoniae pneumonia (SPP). Of these, 59 (30.3%) patients had mixed pneumonia. In patients with mixed SPP, the three most frequent pathogens were influenza virus (27 patients), Haemophilus infuluenzae (14 patients), and Mycoplasma pneumoniae (8 patients). Of these, 21 (35.5%) patients were classified as severe or very severe according to the Japanese Respiratory Society diagnostic criteria among 59 patients of mixed SPP. Severe and very severe pneumonia was significantly associated with mixed infections (P = 0.018). The initial antimicrobial therapy was classified as beta-Lactam alone (113 patients), combination therapy including a beta-Lactam (72 patients), and a fluoroquinolone alone (10 patients). If we limit out study to mild-moderate pneumonia, initial combination therapy was significantly effective in patients with mixed SPP. Even in pneumonia caused by Streptococcus pneumoniae, further efforts to identify etiology are necessary.