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

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• High rates of methicillin resistance observed in Staphylococcus aureus (71.7%) and all coagulase-negative Staphylococcus (CoNS) isolates.
• Teicoplanin is a critical last-resort antibiotic for treating infections caused by resistant strains like MRSA and methicillin-resistant CoNS.

Purpose of the Study:

• To evaluate the accuracy of automated susceptibility testing systems for teicoplanin resistance detection.
• To compare automated testing with broth microdilution (BMD) and gradient test methods for teicoplanin susceptibility.
• To investigate teicoplanin resistance patterns in S. aureus and CoNS isolates.

Main Methods:

• Collected 467 S. aureus and 66 CoNS isolates between June 2022 and December 2024.
• Performed teicoplanin susceptibility testing using an automated system, BMD, and a gradient test.
• Identified methicillin resistance using standard methods.

Main Results:

• Automated systems incorrectly identified 13 S. aureus and 4 CoNS isolates as teicoplanin-resistant.
• All 13 S. aureus isolates were susceptible by gradient test and BMD.
• BMD confirmed teicoplanin resistance in 4 CoNS isolates (1 S. capitis, 3 S. haemolyticus) from blood cultures.

Conclusions:

• Automated systems are unreliable for detecting teicoplanin resistance in Staphylococcus species.
• Broth microdilution (BMD) is essential for confirming teicoplanin resistance, particularly in CoNS.
• Close monitoring of teicoplanin susceptibility is crucial due to its role in treating resistant bacterial infections.