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Vancomycin-dependent Enterococcus faecium isolated from stool following oral vancomycin therapy
L L Dever1, S M Smith, S Handwerger
1Infectious Diseases Section, Veterans Affairs Medical Center, East Orange, New Jersey 07018, USA.
Journal of Clinical Microbiology
|October 1, 1995
Summary
A novel strain of vancomycin-dependent Enterococcus faecium was isolated from a patient. This vancomycin-dependent enterococci strain evolved from vancomycin-resistant bacteria under vancomycin pressure.
Area of Science:
- Microbiology
- Antimicrobial Resistance
Background:
- Vancomycin is a critical antibiotic for treating serious Gram-positive bacterial infections.
- Emergence of vancomycin resistance in enterococci poses a significant clinical challenge.
- Vancomycin-dependent enterococci are rarely reported clinical isolates.
Observation:
- A patient who completed vancomycin therapy yielded vancomycin-dependent Enterococcus faecium in stool.
- This vancomycin-dependent E. faecium strain grew with ristocetin and D-alanyl-D-alanine.
- Spontaneous vancomycin-independent revertants emerged at a rate of 10^-6.
Findings:
- Both vancomycin-dependent E. faecium and revertants contained the vanB gene.
- Identical contour-clamped homogeneous electrophoresis patterns were observed for both strains.
- Revertant colonies predominantly exhibited teicoplanin resistance, indicating constitutive vanB ligase production.
Implications:
- Vancomycin-dependent enterococci may evolve from vancomycin-resistant strains under selective antibiotic pressure.
- Understanding the mechanisms of vancomycin dependence is crucial for infection control.
- This finding highlights the adaptability of enterococci in response to antimicrobial therapy.