Background : Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are very prevalent nosocomial pathogens, often resistant to multiple drugs including various aminoglycosides. Arbekacin is an aminoglycoside used for the treatment of MRSA infections in Japan. The aim of study was to compare the activities of arbekacin against the MRSAs isolated currently and at the start of the spread, and against the selected isolates of P. aeruginosa susceptible or resistant to amikacin, ceftazidime, impenem and ciprofloxacin.
Methods : The strains were isolated from Severance Hospital. The NCCLS disk diffusion and agar dilution tests were used and strains inhibited by 4 ㎍/mL of arbekacin was interpreted as susceptible and 16 ㎍/mL resistant.
Results : Arbekacm ≤4 ㎍/mL inhibited all of the MRSAs tested. The MiC_(90)s for MRS4s isolated in 1980 and 1996 were equal; 2 ㎍/mL, while that for MSSA was 0.5 ㎍/mL. All of the MRSA were susceptible. The resistance rates. in descending order, were to kanamycin, gentamicin, tobramj-cin, amikacin and isepamicin. MIC,, of arbekacin for amikacin-susceptible P. aerugznosa m-as slightly higher than that of amikacin, but slightly lower than those for the strains both susceptible and resistant to ceftazidxme, imipenem and ciprofloxacin. Depending on the susceptibility groups of strains, approximate15 1/3 to 2/3 were susceptible to arbekacin.
Conclusion : Arbekacin may be useful for the treatment of single MRSA infection and for some of the mixed infections of MRSA and P. aerugznosa.