Inability to adequately control antimicrobial agents on AutoMicrobic System Gram-Positive and Gram-Negative...

Area of Science:

• Clinical Microbiology
• Antimicrobial Susceptibility Testing

Background:

• Accurate antimicrobial susceptibility testing is crucial for guiding patient treatment.
• Automated systems like the AutoMicrobic System (AMS) aim to standardize and expedite susceptibility testing.
• The Vitek Gram-Positive Susceptibility Card (GPS) and Gram-Negative General Susceptibility Plus Card (GSC Plus) are widely used for this purpose.

Purpose of the Study:

• To evaluate the performance and reliability of the Vitek GPS and GSC Plus cards on the AMS.
• To determine the extent to which antimicrobial agents on these cards can be adequately controlled using standard methods.

Main Methods:

• The Vitek GPS and GSC Plus cards were tested 50 times each using recommended control organisms on the AutoMicrobic System (AMS).
• Performance was assessed based on the ability to achieve adequate control for each antimicrobial agent included on the cards.

Main Results:

• Only chloramphenicol on the GPS card and gentamicin on the GSC Plus card demonstrated adequate control.
• Results for 10 of 11 drugs on the GPS card and 9 of 10 drugs on the GSC Plus card were not adequately controlled.
• This indicates a significant lack of reliability for the majority of antimicrobial agents tested.

Conclusions:

• The Vitek GPS and GSC Plus cards, when used with the AMS, exhibit poor performance for most antimicrobial agents tested.
• The limited number of adequately controlled drugs raises concerns about the validity of results for patient isolates using the remaining agents.
• Further validation and potential revisions of these susceptibility testing cards are warranted to ensure reliable clinical data.