[Methicillin-resistant Staphylococcus aureus (MRSA) infection--significance of MRSA in respiratory tract infection].

We have examined background factors in MRSA infection in cases in which S. aureus had been isolated from sputa. The incidence of isolation of S. aureus was high and still increasing in expectorated sputa, and causative organisms in the cases of pneumonia and autopsied lungs. A significant correlation was observed between high incidence of isolation of S. aureus and abuse of third-generation cephems. MRSA isolation rates of inpatients was higher than that of outpatients. Among the inpatients such cases with severe underlying diseases and prolonged admission showed the highest incidence of isolation of MRSA. There seemed to be a correlation between distribution of patients with S. aureus and that of rooms with S. aureus in the air. This suggests nosocomial infection. Although MRSA was frequently isolated from sputa, most cases showed no signs of infection, and this suggested that they had been transient colonization. Such antimicrobial agents as rifampicin, teicoplanin, vancomycin reveal excellent antibacterial activity against MRSA and minocycline, ofloxacin were moderately effective. The physician must be informed of the significance of MRSA, because their understanding of MRSA still remains insufficient.