Abstract:

Objective To evaluate the in vitro bactericidal activity of recombinant lysostaphin against Staphylococcus aureus isolated from burn wounds. Methods One hundred and seventy-one Staphylococcus aureus strains were isolated from burn wounds. The minimum inhibitory concentrations (MIC) of vancomycin, erythromycin, clindamycin, cefoxitin and sulfamethoxazole, which were common drugs used for burns in clinics against Staphylococcus aureus were measured by agar dilution method. Methicillin-resistant Staphylococcus aureus (MRSA) and methicillinsensitive Staphylococcus aureus (MSSA) were divided according to the MIC of cefoxitin. Drug resistance analysis of Staphylococcus aureus was conducted according to the results of antimicrobial susceptibility tests of vancomycin, erythromycin, clindamycin and sulfamethoxazole. The MIC of recombinant lysostaphin against Staphylococcus aureus was measured by micro-broth dilution method, and 50% minimun inhibitory concentration (MIC50) and 90% minimun inhibitory concentration (MIC90) were calculated. Results According to the results of antimicrobial susceptibility tests, the resistance rates of Staphylococcus aureus to sulfamethoxazole, erythromycin, clindamycin and vancomycin were 99.4%, 88.3%, 87.1% and 0 respectively, and the prevalence of MRSA was 85.4%(146 strains). The MIC of recombinant lysostaphin against Staphylococcus aureus ranged from 0.015 to 0.5 U/mL, with MIC50 of <0.015 U/mL and MIC90 of 0.03 U/mL. Conclusion Recombinant lysostaphin has favorable in vitro bactericidal activity against Staphylococcus aureus. With the increasing resistance of Staphylococcus aureus to clinical drugs, recombinant lysostaphin may potentially be a potent drug for Staphylococcus aureus infection of the burn wounds.

Key words: recombinant lysostaphin, Staphylococcus aureus, in vitro antibacterial activity, minimal inhibitory concentration, burn wound