Antimicrobial therapy in community-acquired pneumonia among emergency patients in a university hospital in Japan.

As antimicrobial therapy for pneumonia has not been well established in Japan, this study was designed to obtain a more definitive standard for antimicrobial treatment of this condition. Two hundred and thirty-one emergency patients admitted to Kyorin University Hospital between January 1998 and December 2000 were retrospectively analyzed in respect to their age, underlying disease, causative organism, and primary treatment with antimicrobial agent. Furthermore, the severity and prognosis were analyzed for those patients who had not responded to initial treatment with antimicrobial agents. The majority of the patients were elderly (over 65 years old; mean overall age 66.7 +/- 15.2 years) and had severe pneumonia; underlying diseases were recognized at a high rate in patients with severe pneumonia (P < 0.05) and in those classified as elderly (P < 0.0001). The most common underlying conditions in elderly patients were respiratory, cardiovascular (P < 0.01), and cerebrovascular (P < 0.05) diseases. The most common causative organisms were Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae, and Mycoplasma pneumoniae. In patients with severe pneumonia, S. aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa were identified as the most common causative organisms. Complications associated with antimicrobial treatment were observed in those patients with K. pneumoniae isolates who also had severe pneumonia and were frequently treated with penicillin. Furthermore, increased mortality rates were observed in patients not responding well to the initial treatment with antimicrobial agents. Thus, the selection of appropriate initial antimicrobial agents is an important factor affecting the prognosis of patients with community-acquired pneumonia.