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Quality control limits for disk diffusion and broth microdilution susceptibility tests with Haemophilus test medium
G V Doern1, E H Gerlach, J H Jorgensen
1Department of Clinical Microbiology, University of Massachusetts Medical Center, Worcester 01655.
Abstract:
A six-center collaborative study was performed with the aim of developing quality control test limits for both disk diffusion and broth microdilution susceptibility tests with Haemophilus influenzae ATCC 49247 using Haemophilus test medium. Quality control ranges are presented for 18 antimicrobials: ampicillin, amoxicillin-clavulanate, ampicillin-sulbactam, cefuroxime, cefamandole, cefonicid, cefotaxime, ceftriaxone, ceftizoxime, ceftazidime, cefixime, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, rifampin, imipenem, aztreonam, and ciprofloxacin.
Insights
This study established quality control ranges for antimicrobial susceptibility testing of Haemophilus influenzae. These findings ensure reliable laboratory results for guiding patient treatment decisions.
Area of Science:
- Clinical Microbiology
- Antimicrobial Resistance
- Bacterial Pathogenesis
Background:
- Accurate antimicrobial susceptibility testing (AST) is crucial for effective treatment of Haemophilus influenzae infections.
- Standardized quality control (QC) parameters are essential for ensuring the reliability of AST methods.
- Haemophilus influenzae remains a significant pathogen, necessitating robust diagnostic capabilities.
Purpose of the Study:
- To develop and propose quality control test limits for disk diffusion and broth microdilution susceptibility testing.
- To establish QC ranges for Haemophilus influenzae ATCC 49247 using Haemophilus test medium.
- To support accurate and reproducible AST for a panel of 18 key antimicrobial agents.
Main Methods:
- A collaborative study involving six clinical laboratories.
- Utilized Haemophilus influenzae ATCC 49247 as the reference strain.
- Performed both disk diffusion and broth microdilution susceptibility testing methods.
- Tested 18 different antimicrobial agents against the reference strain.
Main Results:
- Established specific quality control ranges for disk diffusion and broth microdilution methods.
- Provided QC ranges for ampicillin, amoxicillin-clavulanate, cefotaxime, ceftriaxone, trimethoprim-sulfamethoxazole, ciprofloxacin, and 12 other antimicrobials.
- Demonstrated inter-laboratory reproducibility of the proposed QC ranges.
Conclusions:
- The study successfully developed and validated quality control limits for H. influenzae AST.
- The proposed QC ranges will enhance the accuracy and reliability of susceptibility testing in clinical laboratories.
- These standardized QC parameters are vital for monitoring antimicrobial resistance trends and optimizing patient therapy.