Antibiotic determination of antibiotic susceptibility testing disks using liquid chromatography and microbiological assay

Introduction: The aim of this work was to control the quality of some antibiotics cartridges (ampicillin, amoxicillin-clavulanic acid, ciprofloxacin and vancomycin) used for antibiotic susceptibility testing by disk diffusion method. Antibiotics were determined in disks and two techniques were compared for this purpose, chromatographic and microbiological method. Methods: Chromatographic method (High-Performance Liquid Chromatography: HPLC) was used for determining ampicillin, amoxicillin-clavulanic acid and ciprofloxacin, and microbiological method for vancomycin and ampicillin. We used the European Pharmacopoeia 8th edition monographs and a simple and adapted method published in 2015 by Ramli Y. et Al. Results: Dosage results reveal that 35% of unexpired cartridges had low content and all the expired AB’s disks gave low results. Conclusion: Our study demonstrated that the content of antibiotics in disks could decrease if the storage and transport conditions (temperature and relative humidity) of disk cartridges were not respected. Therefore, properly performed quality control of antibiotic disks before use in laboratories would aid in providing accurate and reproducible results of dosage. Keywords: Antibiotic disks, Quality control, Antibiogram, High Performance Liquid Chromatography, Microbiological method.