Intracellular activity of antimicrobial compounds used for Staphylococcus aureus nasal decolonization

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Staphylococcus aureus invades mammalian cells during infection.
• Intracellular S. aureus has been detected in the nasal mucosa of healthy carriers.
• The role of intracellular bacteria in nasal colonization is increasingly recognized.

Purpose of the Study:

• To evaluate the efficacy of antimicrobial compounds against intracellular S. aureus.
• To assess the activity of nasal decolonization agents in a relevant cell model.
• To compare the effectiveness of different antimicrobial classes against intracellular bacteria.

Main Methods:

• Developed a HaCaT cell model mimicking S. aureus nasal epithelium invasion.
• Utilized confocal laser scanning microscopy to detect intracellular S. aureus.
• Tested 21 antimicrobial compounds, including mupirocin and chlorhexidine, for intracellular activity.

Main Results:

• Both HaCaT cells and human nasal epithelial cells (HNECs) internalized S. aureus.
• Most tested antimicrobial compounds demonstrated limited activity against intracellular S. aureus.
• Systemic antimicrobials (e.g., fluoroquinolones, clindamycin) significantly reduced intracellular S. aureus loads (0.43-1.66 log cfu/10^6 cells).
• Mupirocin and chlorhexidine showed minimal reduction in intracellular S. aureus (0.19 and 0.23 log cfu/10^6 cells, respectively).

Conclusions:

• Current nasal decolonization agents, including mupirocin and chlorhexidine, have poor efficacy against intracellular S. aureus.
• Systemic antimicrobials show greater potential for targeting intracellular S. aureus reservoirs.
• Further research is needed to understand the intracellular reservoir's role in nasal colonization and to develop improved decolonization strategies.