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Susceptibility of methicillin-resistant Staphylococcus aureus clinical isolates to various antimicrobial agents
1Institute of Pharmaceutical Sciences, Hiroshima University School of Medicine, Japan.
Abstract:
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% (beta-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.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) showed high resistance to common antibiotics. However, strains remained susceptible to vancomycin and arbekacin, with emerging resistance to tetracyclines and fluoroquinolones observed.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global health threat.
- Understanding MRSA resistance patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the antimicrobial resistance profiles of MRSA strains isolated in Japan.
- To identify trends in resistance over time and assess susceptibility to various antibiotic classes.
Main Methods:
- Phenotypic characterization of 42 MRSA strains against 23 antimicrobial agents.
- Analysis of resistance patterns from strains collected between 1984-1990 in Hiroshima and Tokushima.
Main Results:
- 100% resistance to methicillin, beta-lactams (flomoxef), and macrolides (erythromycin, clarithromycin).
- High resistance observed for aminoglycosides (kanamycin, tobramycin, amikacin) and fosfomycin.
- Complete susceptibility to vancomycin and arbekacin; variable resistance to fluoroquinolones and tetracyclines.
- Emerging resistance to tetracyclines and fluoroquinolones noted in later isolates, alongside a decrease in mikamycin B resistance.
Conclusions:
- MRSA strains exhibit extensive resistance to clinically used antibiotics.
- Vancomycin and arbekacin remain effective against these MRSA strains.
- Monitoring resistance trends, particularly to fluoroquinolones and tetracyclines, is essential for guiding empirical therapy.