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Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence
G L French1, A F Cheng, J M Ling
1Department of Microbiology, Chinese University of Hong Kong, Shatin.
Abstract:
While most authorities agree that methicillin-resistant Staphylococcus aureus (MRSA) are as pathogenic as methicillin-sensitive strains (MSSA), some believe that MRSA are relatively avirulent opportunists, and that their importance has been exaggerated. We present evidence that Hong Kong strains of MRSA and MSSA are equally pathogenic: they have similar virulence in animal models; they are isolated in similar proportions from both deep and superficial clinical sites including blood; in patients with hospital-acquired bacteraemias mortality rates are similar when adjusted for clinical factors; and in both animals and patients with systemic MRSA infection, mortality rates are significantly reduced by vancomycin therapy. Efforts to control the spread of MRSA are justified, and in invasive sepsis early treatment with vancomycin may be life-saving.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) show similar pathogenicity. Controlling MRSA spread is crucial, and vancomycin is vital for treating invasive MRSA infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Debate exists regarding the pathogenicity of methicillin-resistant Staphylococcus aureus (MRSA) compared to methicillin-sensitive Staphylococcus aureus (MSSA).
- Some suggest MRSA are opportunistic pathogens whose significance may be overstated.
Purpose of the Study:
- To investigate and compare the pathogenicity of Hong Kong strains of MRSA and MSSA.
- To provide evidence supporting the need for MRSA control measures.
Main Methods:
- Virulence assessment in animal models.
- Analysis of isolation proportions from various clinical sites, including blood.
- Comparison of mortality rates in hospital-acquired bacteremia, adjusted for clinical factors.
- Evaluation of vancomycin therapy efficacy in systemic MRSA infections.
Main Results:
- MRSA and MSSA demonstrated similar virulence in animal models.
- Both strains were isolated in comparable proportions from deep and superficial clinical sites.
- Adjusted mortality rates for hospital-acquired bacteremia were similar between MRSA and MSSA.
- Vancomycin therapy significantly reduced mortality rates in both animals and patients with systemic MRSA infections.
Conclusions:
- MRSA and MSSA strains from Hong Kong exhibit comparable pathogenicity.
- Controlling the spread of MRSA is scientifically justified.
- Early vancomycin treatment is critical for improving outcomes in invasive MRSA sepsis.