[Antibacteriological activities of arbekacin and vancomycin against strains of MRSA]

The activities of arbekacin (ABK) and vancomycin (VCM) against MRSA were compared, and the results are as follows. 1. In antibacterial activities (MIC value) against 142 strains of MRSA, MIC50 of ABK was two times less than that of VCM. MIC90's were both 1.56 micrograms/ml. 2. ABK was also superior to VCM in bactericidal activities within a short time against 100 strains of MRSA. After 4 hours, 42 strains were killed to below 10(-2) by 2 MIC of ABK, but 6 strains were killed to 10(-2) by 4 MIC of VCM. 3. Against the MRSA 1936 strain, neither ABK nor VCM was active, when an inoculum size of about 10(8) CFU/ml was used. At an inoculum size of 10(5) CFU/ml, ABK showed strong bactericidal activity in a dose dependent manner, while bacteria killing activity of VCM was time dependent. 4. In experimental infections with the MRSA 1936 strain, ABK showed high bactericidal activity rapidly, and area of body that showed bacterial inhibition appeared to be large compared to that obtained with VCM. 5. As to protection from MRSA infections, ABK was significantly superior to VCM in activities against 3 out of 4 strains of MRSA tested. ABK showed more pronounced efficacy when administered in a single dose than in divided doses. These results indicated that ABK would exhibit therapeutic efficacy in a short time.