In vitro efficacy and combined drug sensitivity of lycosin-I against methicillin-resistant Staphylococcus aureus / 中华检验医学杂志

ABSTRACT

Objective:The aim of this study was to evaluate the in vitro activity of lysosin-Ⅰ against Methicillin-resistant Staphylococcus aureus (MRSA) and its synergistic effect with eight common antibacterial drugs against MRSA. Methods:This study was conducted following the design principles of a randomized controlled trials. Ten MRSA isolates, clinically isolated from the Second Xiangya Hospital of Central South University between September and November 2021, were determined the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and bactericidal kinetic test of lycosin-Ⅰ in vitro anti-MRSA by micro-broth dilution method. Additionally, the micro-broth chessboard dilution method was utilized to evaluate the in vitro efficacy of lycosin-Ⅰ in combination with eight common antimicrobial agants, including penicillin, erythromycin, levofloxacin, gentamicin, rifampicin, minocycline, vancomycin, and linezolid. Results:The MIC range of lycosin-Ⅰ against MRSA was found to be between 4-8 mg/L with the MIC 50 and MIC 90 were 4 mg/L and 8 mg/L, respectively. The range of MBC was also between 4-8 mg/L, and the ratio of MBC/MIC was 1-2. The bactericidal kinetics test revealed that the number of surviving MRSA clinical isolates and standard strains initially decreased rapidly but then showed a resurgence when the concentration of lycosin-Ⅰ was 1/2 MIC or MIC. While, the bacterial load gradually reduced until complete elimination when the concentration was at 2 MIC or 4 MIC. The combination of lycosin-Ⅰ and gentamicin exhibited mainly synergistic effects, while the combination with other antibiotics showed mainly additive effects. Moreover, the combination of lycosin-Ⅰ and antibacterial drugs can significantly reduce the MIC 50 and MIC 90 of antibiotics. Conclusion:lycosin-Ⅰ has great antibacterial and bactericidal activity against MRSA in vitro with rapid and thorough sterilization effect and it can play a synergistic or additive role when combined with other antibacterial drugs against MRSA in vitro.