A simplified and accurate approach to agar diffusion antibiotic assay

Area of Science:

• Microbiology
• Analytical Chemistry
• Pharmaceutical Sciences

Background:

• Current linear microbiological assays for antimicrobial susceptibility test (AST) discs fail with curved calibration lines.
• Multipoint assays are an alternative but are difficult to implement and rarely used.
• A need exists for a simpler three-point assay method accommodating non-linear relationships.

Purpose of the Study:

• To introduce a novel data transformation method for a three-point assay in AST disc calibration.
• To enable straight-line calibration, avoiding complex multipoint assays.
• To enhance the accuracy and reliability of AST disc quality.

Main Methods:

• The study employed data transformation techniques to linearize calibration curves.
• Two literature examples with quadratic and cubic fits were re-analyzed using the new method.
• The transformed data yielded a straight-line calibration for improved assay accuracy.

Main Results:

• The data transformation method successfully created a straight-line calibration from non-linear data.
• Reworked examples demonstrated more accurate assay results compared to previous analyses.
• The method proved effective for both quadratic and cubic non-linear fits.

Conclusions:

• The described three-point assay method offers a cost-effective and straightforward approach to AST disc calibration.
• This technique enhances the quality of antimicrobial susceptibility test discs.
• Improved AST disc quality has the potential to positively impact clinical outcomes.