Seeking vancomycin resistant Staphylococcus aureus among patients with vancomycin-resistant enterococci

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.