Antimicrobial susceptibility testing by broth microdilution method: widely available modification

Abstract

Objective. To assess the possibility of standard disk application as an antibiotic source for determination of the minimal inhibitory concentrations (MICs) by serial microdilution method. Materials and Methods. A simple method of working solutions preparation using standard paper discs as an antibiotics source available in most microbiological laboratories is proposed. A multiple determination of antibiotic MICs for E. coli ATCC 25922 and P. aeruginosa ATCC 27853 strains was conducted. Results. Of the 576 MIC values determined by the modified method, 78.5% of the results corresponded to the control strains reference values, and 20.8% of the results were categorized as acceptable values. Conclusions. Use of standard disks as an antibiotics source for the working solutions preparation greatly simplifies a testing by serial microdilution method and makes it available to most microbiological laboratories.

Keywords

• minimal inhibitory concentration
• disks with antibiotics
• antimicrobial resistance