Zone of Inhibition Test: Assay for Treated Articles

Purpose of the Zone of Inhibition Test

A zone of inhibition assay for treated materials is a carrier-based, presumptive test method designed to quickly determine antimicrobial activity of diffusible antimicrobial agents on treated articles. As an adaptation from the Clinical and Laboratory Standards Institute (CSLI) Antimicrobial Susceptibility Testing, this method is generally used to screen for presumptive antimicrobial activity ultimately used for non-public health related claims.

Summary of the Zone of Inhibition Test

In this method, agar plates are inoculated with a lawn of test organism. The treated samples are placed over the inoculated plate and are incubated. Following incubation, the samples are visually examined for zones of clearing and the treated materials are compared to the untreated control materials to draw conclusions about the degree of antimicrobial activity observed. No regulated limits currently exist for general antimicrobial claims made using this method.