Staphylococcus aureus with reduced susceptibility to vancomycin in healthcare settings

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Glycopeptide resistance in Staphylococcus aureus is a major clinical concern, particularly for treating Methicillin-Resistant Staphylococcus aureus (MRSA) infections.
• Vancomycin is a critical antibiotic for MRSA, but reduced susceptibility, including Vancomycin-Intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (h-VISA), compromises treatment.
• h-VISA isolates contain a resistant subpopulation, representing an intermediate stage between susceptible strains (VSSA) and fully resistant strains (VISA).

Purpose of the Study:

• To highlight the clinical significance of heterogeneous glycopeptide resistance in Staphylococcus aureus.
• To emphasize the challenges posed by h-VISA/h-GISA strains in clinical settings.
• To underscore the importance of implementing robust infection control strategies.

Main Methods:

• Phenotypic characterization of Staphylococcus aureus isolates.
• Assessment of vancomycin and teicoplanin susceptibility.
• Prevalence and mortality data analysis for h-VISA/h-GISA strains.

Main Results:

• h-VISA strains exhibit a resistant subpopulation (approx. 1 in 10^5 organisms).
• VISA phenotypes are often cross-resistant to teicoplanin, termed GISA (Glycopeptide-Intermediate Staphylococcus aureus), with heterogeneous forms called h-GISA.
• The prevalence of h-VISA is low (approx. 1.3% of MRSA isolates), but associated with very high mortality (approx. 70%), especially in ICUs.

Conclusions:

• h-VISA/h-GISA strains represent a critical intermediate step in glycopeptide resistance.
• Effective infection control, including surveillance, isolation, hygiene, and antibiotic stewardship, is crucial.
• Addressing h-VISA/h-GISA is vital to mitigate treatment failures and improve patient outcomes.