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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

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Increased oxacillin activity associated with glycopeptides in coagulase-negative staphylococci

B E Domaracki1, A Evans, K E Preston

  • 1Department of Pathology and Laboratory Medicine, Albany Medical Center, New York 12208, USA.

European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology
|July 17, 1998
PubMed

Insights

Developing vancomycin resistance in staphylococci unexpectedly increased susceptibility to beta-lactam antibiotics. This finding challenges current understanding and suggests new therapeutic strategies for resistant bacterial infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antibiotic Resistance

Background:

  • Methicillin-resistant staphylococci (MRS) pose significant therapeutic challenges due to antibiotic resistance.
  • Vancomycin resistance in staphylococci is a growing concern, potentially limiting treatment options.

Purpose of the Study:

  • To investigate the impact of low-level vancomycin resistance on coagulase-negative staphylococci (CoNS).
  • To explore the relationship between vancomycin resistance and susceptibility to other antibiotics, particularly beta-lactams.

Main Methods:

  • Stepwise selection of vancomycin resistance in Staphylococcus haemolyticus and Staphylococcus epidermidis using increasing vancomycin concentrations.
  • Analysis of genetic and phenotypic markers including mecA gene presence, RFLP, beta-lactamase production, and protein fractions.
  • Evaluation of oxacillin susceptibility and checkerboard assays to assess synergistic effects of vancomycin and oxacillin combinations.

Main Results:

  • Selected vancomycin-resistant Staphylococcus haemolyticus clones showed a >40-fold increase in susceptibility to beta-lactam antibiotics.
  • No significant changes were observed in growth curves, mecA gene, RFLP, beta-lactamase production, or protein profiles.
  • Clinical isolates of CoNS exposed to sub-inhibitory concentrations of vancomycin or teicoplanin lost high-level oxacillin resistance.
  • Synergistic activity between vancomycin and oxacillin was observed in several CoNS isolates.

Conclusions:

  • Inducing low-level vancomycin resistance in CoNS can paradoxically enhance susceptibility to beta-lactam antibiotics.
  • This phenomenon suggests complex adaptive mechanisms in staphylococci and potential for novel therapeutic approaches.
  • Combination therapy with vancomycin and oxacillin may be effective against certain resistant staphylococcal strains.

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