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Seeking vancomycin resistant Staphylococcus aureus among patients with vancomycin-resistant enterococci
Abstract:
Clinical isolates of Staphylococcus aureus displaying intermediate resistance to vancomycin (VISA) have been identified. The objective of our study was to identify VISA colonization among patients known to be colonized or infected with vancomycin-resistant enterococci (VRE). Eight weekly point prevalence screening surveys for VRE and S. aureus were conducted on 5 hospital units. Of the 243 patients screened, 31 (12.8%) were colonized with VRE. In addition, 18 inpatients were already known to be VRE-positive. Fourteen (28.6%) of the 49 VRE-positive patients were co-colonized with S. aureus. All 30 S. aureus isolates from these 14 patients were methicillin-resistant (MRSA) but remained vancomycin-susceptible (minimal inhibitory concentration [MIC] range, 0.75-2 microg/mL). Population analysis profiling demonstrated no evidence of heteroresistant subpopulations that could grow on agar containing 3 microg/mL vancomycin for any of the MRSA isolates. Although 23 (77%) of 30 staphylococcal isolates had vancomycin MICs of 1.5 or 2 microg/mL, no VISA strains (MICs, 8-16 microg/mL) were recovered.
Insights
This study investigated vancomycin-intermediate Staphylococcus aureus (VISA) colonization in patients with vancomycin-resistant enterococci (VRE). No VISA strains were found, indicating low risk of this co-colonization in VRE patients.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Medicine
Background:
- Clinical isolates of vancomycin-intermediate Staphylococcus aureus (VISA) have emerged.
- Vancomycin-resistant enterococci (VRE) colonization is a significant healthcare concern.
- Co-colonization of VRE and S. aureus presents potential challenges in infection control.
Purpose of the Study:
- To determine the prevalence of VISA colonization in patients already colonized or infected with VRE.
- To assess the risk of S. aureus acquiring vancomycin resistance in the presence of VRE.
Main Methods:
- Eight weekly point prevalence surveys were conducted across five hospital units.
- Screening included VRE and Staphylococcus aureus (S. aureus) detection.
- S. aureus isolates underwent methicillin resistance testing and vancomycin susceptibility testing (MICs).
- Population analysis profiling was used to detect heteroresistant subpopulations.
Main Results:
- Of 243 patients screened, 31 (12.8%) were VRE-positive, with 18 additional known VRE-positive inpatients.
- Fourteen (28.6%) of 49 VRE-positive patients were co-colonized with S. aureus.
- All 30 S. aureus isolates were methicillin-resistant (MRSA) but vancomycin-susceptible (MICs 0.75-2 µg/mL).
- No VISA strains (MICs 8-16 µg/mL) were recovered; population analysis showed no heteroresistance.
Conclusions:
- No vancomycin-intermediate Staphylococcus aureus (VISA) was detected in VRE-colonized patients.
- Methicillin-resistant S. aureus (MRSA) co-colonization in VRE patients remained susceptible to vancomycin.
- The risk of VISA development or co-colonization in this patient population appears low based on this study.