The Glycopeptide-Susceptibility of Multidrug-Resistant/Extensively Drug-Resistant Staphylococcus aureus in Skin Infections

Background: The prevalence of drug-resistant Staphylococcus aureus is increasing alarmingly, limiting treatment options. Objectives: This study was conducted to investigate the minimum inhibitory concentration (MIC) of glycopeptides against multidrug-resistant (MDR) and extensively drug-resistant (XDR) S. aureus isolates from patients with skin infections. Methods: In this study, S. aureus isolates were collected from outpatients with skin infections (n = 250) during 2019 - 2022. The isolates were identified using routine microbiological and biochemical tests. Susceptibility to ten categories of antibacterial agents was assessed using the Kirby-Bauer method according to the Clinical and Laboratory Standards Institute M100 guidelines (2021). The MIC of glycopeptides was determined using the broth microdilution test. Results: Among methicillin-resistant S. aureus isolates (40.8%), the majority were from patients with impetigo (53.92%). The highest resistance rate was observed against penicillin (79.41%) and doxycycline (73.52%). Linezolid showed significant inhibitory properties against XDR (91%) and MDR (97%) S. aureus isolates (P = 0.01). The MIC of oritavancin that inhibited the growth of 90% of the MDR isolates (MIC90) was 2 µg/mL, which was eight times less than that of vancomycin (MIC90 = 16 µg/mL) and 16 times lower than that of teicoplanin (MIC90 = 32 µg/mL) in a manner that 91% of MDR isolates from impetigo were eliminated at concentrations 2 µg/mL. Oritavancin inhibited the growth of 54.5% of XDR isolates at MIC concentrations of ≥8 µg/mL. Conclusions: Considering the strong antibacterial activity of linezolid against MDR S. aureus isolates, this antibiotic can effectively treat skin infections caused by S. aureus and prevent the development of resistance to other antibiotics. In addition, considering the great inhibitory properties of oritavancin against MDR S. aureus strains, the efficacy of this agent for treating skin infections, particularly impetigo, should be investigated.