[Drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) in Japan until 1993]

Isolation frequency of MRSA in Japan increased up to 60% until 1993. The therapy of infectious diseases usually begins empirically, then doctors would verify or change their regimen according to laboratory data. But the hospital-infected MRSA strains are now highly resistant to beta-lactams, and strains resistant to other antibiotics such as, macrolides, quinolones and minocycline are also increasing. MRSA strains in infected focus are often mixtures of strains expressing different patterns of multiple resistance, and often exist with other pathogens such as Pseudomonas aeruginosa. Relying upon laboratory data alone, often results in emergence of new resistant bacteria or replacement of pathogens, hence ineffectiveness of chemotherapy. Now only arbekacin and vancomycin are the antibiotics to which resistant strains are less than 3%. Other antibiotics should be used after considering the resistance pattern of isolates from the patient and in the hospital. Most of the MRSA-infected patients are compromised hosts, and the in vivo efficacy does not always reflect the in vitro results. Even arbekacin and vancomycin are sometimes recommended to be used in combination therapies with other drugs.