Antimicrobial activity of different antimicrobial peptides (AMPs) against clinical methicillin-resistant Staphylococcus aureus (MRSA).

Background: Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In this direction, antimicrobial peptides (AMP) appear as promising tool. Objectives: This study evaluated the antimicrobial activity of different AMPs (Citropin 1.1, Temporin A, Pexiganan, CA(1-7)M(2-9)NH2, Pal-KGK-NH2, Pal-KKKK-NH2, LL-37) against human MRSA clinical isolates. Methods: The Minimum Inhibitory Concentration (MIC) was assessed for each AMP; then, the most active ones (Citropin 1.1, Temporin A, CA(1-7)M(2-9)NH2 and Pal-KGK-NH2) were tested against selected MRSA strains by time-kill studies. Results: The lowest MIC value was observed for Pal-KGK-NH2 (1 mu g/ml), followed by Temporin A (4-16 mu g/ml), CA(1-7)M(2-9)NH2 (8-16 mu g/ml) and Citropin 1.1 (16-64 mu g/ml), while higher MICs were evidenced for LL-37, Pexiganan and Pal-KKKK-NH2 (> 128 mu g/ml). In time-kill experiments, Citropin 1.1 and CA(1-7)M(2-9)NH2 showed a relatively high percentage of growth inhibition (>30 %) for all the tested MRSA clinical isolates, with a dose-dependent activity resulting in the highest percentage of bacterial growth inhibition (89.39 A) at 2MIC concentration. Conclusion: Overall, our data demonstrated the potential of some AMPs against MRSA isolates, such as Citropin 1.1 and CA(1-7)M(2-9)NH2, that represents a promising area of development for different clinical applications.