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Updated: May 4, 2026
Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus MRSA in Rat
Published on: June 4, 2012
hVISA and MRSA endocarditis: an 8-year experience in a tertiary care centre
Y Maor1, N Belausov, D Ben-David
1Infectious Disease Unit, Sheba Medical Centre, Tel Hashomer, Israel; Tel Aviv University, Tel Aviv, Israel.
Abstract:
It is not clear if patients with heterogeneous intermediate resistance to vancomycin (hVISA) infectious endocarditis (IE) differ from methicillin-resistant S. aureus (MRSA) IE patients. All cases of hVISA and MRSA IE diagnosed at the Sheba Medical Centre from 2003 to 2010 were included. Isolates were screened prospectively for hVISA. Medical records were reviewed. The t-test, chi-square test, Fisher exact test and Kaplan Meier analysis were used. Fourteen hVISA IE and 32 MRSA IE were identified. The mean age was 76 years, mean Charlson score was 4.5 and 24% of patients had prosthetic valves. Pacemakers and implantable cardioverter-defibrillators (P/ICDs) were more common in the hVISA group (50% vs. 22%, p 0.05). P/ICDs IE occurred in 29% of hVISA patients vs. 6.3% of MRSA patients (p 0.06). hVISA patients had more positive blood cultures (eight vs. five, p 0.007) and a trend toward longer bacteraemia (15 vs. 7.5 days, p 0.08). Vancomycin minimal inhibitory concentrations (MICs) were similar in the two groups (1.5 μg/mL vs. 1.1 μg/mL, p 0.11). The MIC to daptomycin was higher in hVISA (0.75 μg/mL vs. 0.32 μg/mL, p 0.049). MRSA patients received vancomycin. hVISA patients were switched to other antibiotics. Cardiac surgery and/or P/ICD extraction was performed more commonly in hVISA patients (50% vs. 16%, p 0.027). Mortality was high in both groups (57-66%). The median time to death was 39 days in the hVISA group and 19 days in the MRSA group (p 0.3). hVISA IE is associated with P/ICDs. Both hVISA and MRSA are associated with high mortality. Low rates of surgical intervention and P/ICD extraction reflect the high co-morbidity of patients. Caution should be employed in the empirical use of daptomycin in hVISA patients.
Insights
Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) infectious endocarditis (IE) is linked to pacemakers and implantable cardioverter-defibrillators (P/ICDs). Both hVISA and methicillin-resistant S. aureus (MRSA) IE exhibit high mortality, necessitating careful antibiotic selection.
Area of Science:
- Infectious Diseases
- Cardiology
- Clinical Microbiology
Background:
- Distinguishing clinical characteristics and outcomes between heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) and methicillin-resistant S. aureus (MRSA) infectious endocarditis (IE) is crucial for effective management.
- Previous studies have not clearly defined the differences in patient populations and disease trajectories between hVISA IE and MRSA IE.
Purpose of the Study:
- To compare the clinical features, treatment strategies, and outcomes of patients with hVISA IE versus MRSA IE.
- To identify specific risk factors and complications associated with hVISA IE.
Main Methods:
- A retrospective review of all diagnosed hVISA and MRSA IE cases at Sheba Medical Centre between 2003 and 2010.
- Prospective screening of isolates for hVISA, followed by detailed medical record review.
- Statistical analysis including t-tests, chi-square tests, Fisher exact tests, and Kaplan-Meier survival analysis.
Main Results:
- Fourteen hVISA IE and 32 MRSA IE cases were identified. hVISA patients were more likely to have pacemakers and implantable cardioverter-defibrillators (P/ICDs) (50% vs. 22%, p=0.05) and experienced IE related to these devices more frequently (29% vs. 6.3%, p=0.06).
- hVISA patients presented with more positive blood cultures (eight vs. five, p=0.007) and a trend towards longer bacteremia (15 vs. 7.5 days, p=0.08). Vancomycin MICs were similar, but daptomycin MICs were higher in hVISA isolates (0.75 μg/mL vs. 0.32 μg/mL, p=0.049).
- Cardiac surgery or P/ICD extraction was more common in hVISA patients (50% vs. 16%, p=0.027). Both groups had high mortality rates (57-66%), with a median time to death of 39 days for hVISA IE and 19 days for MRSA IE.
Conclusions:
- hVISA IE is significantly associated with the presence of P/ICDs, suggesting a distinct clinical profile compared to MRSA IE.
- Both hVISA and MRSA IE are associated with substantial mortality, often exacerbated by high patient comorbidity, leading to limited surgical interventions.
- Caution is advised regarding the empirical use of daptomycin in suspected hVISA infections due to potentially higher MICs.
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