Colonization with vancomycin-intermediate Staphylococcus aureus strains containing the vanA resistance gene in a...

Area of Science:

• Microbiology
• Infectious Diseases
• Clinical Medicine

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen, particularly in healthcare settings.
• Vancomycin remains a critical treatment option for MRSA infections.
• Emergence of vancomycin resistance in MRSA is a growing public health concern.

Purpose of the Study:

• To investigate the prevalence and characteristics of MRSA nasal carriage in an intensive care unit (ICU).
• To identify MRSA strains with reduced susceptibility to vancomycin.
• To explore potential genetic mechanisms and factors influencing vancomycin resistance.

Main Methods:

• Conducted a nasal carriage survey for MRSA within an ICU setting.
• Phenotypic screening of MRSA isolates for reduced vancomycin susceptibility.
• Molecular detection of vancomycin resistance genes, specifically the vanA gene.

Main Results:

• Four MRSA strains exhibiting reduced susceptibility to vancomycin were identified.
• The vanA gene, a marker for high-level vancomycin resistance, was detected in two of these vancomycin-intermediate Staphylococcus aureus (VISA) strains.
• The study observed a potential correlation between the absence of selective vancomycin pressure and reduced expression of resistance genes.

Conclusions:

• The presence of VISA strains in ICU nasal carriage highlights the evolving resistance patterns of MRSA.
• The vanA gene in some VISA strains indicates a potential for further resistance development.
• Environmental factors, such as reduced vancomycin usage, might influence the expression and prevalence of vancomycin resistance mechanisms in MRSA.