Introduction: Infection caused by methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) is a serious clinical challenge and research to develop new antimicrobials is imperative.
Methods: This study investigated the in vitro and in vivo efficacy of the short cationic dialkyl lipopeptides (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2. The antibacterial efficacy of (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2 was evaluated in representative clinical methicillin-susceptible S. aureus and MRSA strains by both in vitro (MIC, time-kill curve) and in vivo (wax worms model) approaches.
Results: These studies revealed that both (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2 have rapid bactericidal activity, with a decrease of > 3 log10 colony forming units (CFU)/mL achieved in the first 6 hours of treatment. Furthermore, (C10)2-KKKK-NH2 performed similarly to daptomycin, with a sustained bacterial killing after 24 hours. Wax worms infected and treated with these lipopeptides showed a decreased survival rate of 90% to 50% within the first day of treatment. Scanning electron microscopy determined that the effect of the short lipopeptides in S. aureus was associated with important morphological structural changes that may suggest cell membrane perturbation.
Conclusion: These findings suggest that the short lipopeptides (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2 may be potential new options for treating MRSA infections.
Keywords: Antimicrobial lipopeptides; Galleria mellonella; In vivo infection model; Methicillin-resistant Staphylococcus aureus (MRSA); Staphylococcus aureus; Wax worms.
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