Antimicrobial Activity of Natural Extracts Against Catheter-Colonizing Methicillin-Resistant Staphylococcus aureus Clinical Isolates

<b>Background:</b> Intravascular catheters (ICs) are critical medical devices but require frequent replacement due to the risk of bacterial colonization, which can lead to bloodstream infections. This process causes patient discomfort and incurs significant health and economic costs. <b>Aim:</b> To evaluate the inhibitory activity of natural extracts as potential IC coatings to prevent colonization by methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). <b>Methods:</b> Thirty-six clinical MRSA isolates, obtained from ICs using the Maki technique, were tested. Three natural extracts were evaluated: garlic extract enriched in thiosulfinates (allicin: 7 mg/g), grape extract enriched in proanthocyanidins (92% proanthocyanidins), and propolis extract. Chlorhexidine gluconate (CHG) served as the bactericidal control. The minimum inhibitory concentration (MIC) was determined using the broth microdilution technique with optical density measurements and resazurin-based viability confirmation. The minimum bactericidal concentration (MBC) was assessed from viable cells in wells exceeding the MIC. <b>Results:</b> All tested extracts exhibited bacteriostatic activity against MRSA isolates. The grape extract demonstrated the lowest MIC₉₀ (3.125 mg/mL), followed by propolis extract (MIC₉₀ = 12.5 mg/mL) and garlic extract (MIC₉₀ = 50 mg/mL). Only the propolis extract showed bactericidal activity (MBC = 25 mg/mL). While CHG outperformed the natural extracts, their activity against MRSA suggests potential clinical utility. <b>Conclusion:</b> The natural extracts studied display promising bacteriostatic activity against MRSA isolates from ICs, with propolis extract additionally showing bactericidal effects. Although less potent than CHG, these extracts offer a potential alternative for combating multidrug-resistant pathogens in clinical settings, warranting further investigation for use as IC coatings.