Susceptibility of Methicillin-resistant Staphylococcus aureus Clinical Isolates to Various Antimicrobial Agents

Resistance patterns against 23 antimicrobial agents were examined for 42 strains of methicillin-resistant Staphylococcus aureus (MRSA). Thirty-four strains were isolated at Hiroshima University Hospital during 1984-1990 and 8 strains were collected in Tokushima city in 1986. Overall resistance to the antimicrobial agents in clinical use is summarized as follows: methicillin 100%, flomoxef 93% (β-lactams); kanamycin 98%, tobramycin 88%, amikacin 83%, isepamicin 81 %, gentamicin 60%, dibekacin 64%, arbekacin 0% (aminocyclitol aminoglycosides); ofloxacin 31 %, TA-167 33% (fluoroquinolones); erythromycin 100%, clarithromycin 100%, josamycin 71 % (macrolides); vancomycin 0% (glycopeptide); tetracycline 43%, minocycline 31 % (tetracyclines); fosfomycin 93%. The MRSA strains remained susceptible to the non-clinical peptide group of antibiotics except for mikamycin B: mikamycin A 2%, mikamycin B 69%, nosiheptide 0%, bottromycin A2 0%, bottromycin D-1 0%, bottromycin D-2 0%.　　

Since April 1990, the MRSA strains isolated at Hiroshima University Hospital showed a tendency to acquire resistance to tetracyclines and fluoroquinolones and to lose mikamycin B-resistance.　　

As of August 1990, none of the MRSA strains isolated at Hiroshima University Hospital was resistant to vancomycin and arbekacin.