Is Teicoplanin Resistance Detected By The Automated System In Staphylococcus spp Strains Reliable?

A total of 467 Staphylococcus aureus (S. aureus) and 66 coagulase-negative Staphylococcus (CoNS) isolates collected between June 2022 and December 2024 were included in this study. Teicoplanin susceptibility testing was performed using the automated antimicrobial susceptibility testing system, broth microdilution (BMD), and a gradient test method. Methicillin resistance was detected in 71.7% of S. aureus isolates and in all CoNS isolates. In this study, 13 S. aureus isolates and 4 CoNS isolates were identified as teicoplanin-resistant by automated susceptibility testing system. All 13 S. aureus isolates were found to be susceptible to teicoplanin by both the gradient test and BMD. All four CoNS isolates were identified as susceptible by the gradient test, whereas BMD classified two isolates as susceptible and two as resistant. Teicoplanin resistance was detected in four strains [S. capitis (n = 1) and S. haemolyticus (n = 3)] among the CoNS isolates by BMD. The four teicoplanin-resistant CoNS strains identified by BMD were isolated from blood cultures; three were obtained from pediatric patients and one from an adult patient. Overall, the methicillin-resistant S. aureus (MRSA) rate was relatively high in the study, and all CoNS isolates were methicillin resistant. In addition, automated systems were found to be unreliable for determining teicoplanin resistance, and isolates identified as resistant should be confirmed by BMD. Given that teicoplanin is a last-resort antibiotic used to treat pathogens such as MRSA and methicillin-resistant CoNS, its susceptibility should be closely monitored.