Quality control limits for ampicillin, carbenicillin, mezlocillin, and piperacillin disk diffusion susceptibility...

Area of Science:

• Clinical Microbiology
• Pharmacology

Background:

• Disk diffusion susceptibility testing is crucial for guiding antibiotic therapy.
• Establishing reliable quality control (QC) limits is essential for accurate susceptibility testing.

Purpose of the Study:

• To determine quality control limits for disk diffusion susceptibility testing of mezlocillin and piperacillin.
• To reevaluate existing quality control limits for carbenicillin and ampicillin.

Main Methods:

• A multilaboratory in vitro study involving nine laboratories.
• Testing followed National Committee for Clinical Laboratory Standards (NCCLS) guidelines.
• Mueller-Hinton agar and antibiotic disks from various manufacturers were used.

Main Results:

• No clinically significant differences were observed between disks from different manufacturers.
• Upper and lower control limits were established using median and median range analysis.
• Data showed close agreement with national proficiency testing programs.

Conclusions:

• The proposed method for establishing QC limits is valid for new antimicrobial agents.
• Recommendations for quality control guidelines for mezlocillin and piperacillin were developed.
• The study validates a robust approach for antimicrobial susceptibility testing QC.