Agar diffusion microbiological assay measurement using a smartphone device and its measurement uncertainty using the bootstrapping method

Usually, inhibition zone sizes in agar diffusion microbiological assay of antibiotics are measured using regular callipers. In this study, we proposed the use of a smartphone app for measuring inhibition zone sizes. The smartphone app allows for standardized measurements with a reference scale, which provides measured values comparable to those obtained using regular callipers. The main uncertainty source associated with antibiotic potency is inhibition zone size variability. Here, we suggest using the bootstrapping method, a resampling technique, to estimate measurement uncertainty without complex calculations. This simplifies the process and yields comparable results to the usual measurement uncertainty calculations. Both improvements were successfully applied to determine the potency of gentamicin, linezolid, and cefazolin. The results showed that smartphone-based measurements and the bootstrapping approach are valuable tools in agar diffusion microbiological assays.