Development and Testing of a Rapid Protocol for Environmental Swabs Using an Oxygen-Depletion Technology

Introduction: It is common practice for the equipment and surfaces used in food processing and preparation to be tested for sterility by swabbing. Usually, the recovered microbial load from the swab is submitted for aerobic plate count (APC) testing using either the BAM or ISO methods. The plating methods and subsequent counting activities are manual and prone to error.

Purpose: A new technology has been introduced that can reduce the testing and enumeration time for even low bacterial loads on swabs, to less than 12 hours. A protocol using commercially available swab products has been developed that uses this oxygen depletion technology to reduce preparation time and also testing time while reducing errors.

Methods: In a three-phase program, the protocol was developed to determine the usefulness and typical processing time for swab samples. In Phase One the amount of microbial recovery into the sensing medium was estimated. In Phase Two, sterility validation tests were run in a typical food testing laboratory. Finally, a field trial was conducted in collaboration with a food processor.

Results: Estimated bacterial recovery from the swabs are presented. An instrument calibration curve is determined and statistical results from the lab and field trials are tabulated. 1) Bacterial recovery from selected swabs is confirmed to exceed 80%; 2) Correlation to the reference method in a controlled test is confirmed to be greater than 0.92; 3) Correlation to the reference method in a field study is confirmed to be greater than 0.92; and 4) Time to result is confirmed to be reduced by 75% versus the reference method.

Significance: This new method reduces the waiting time for swab results while also reducing the amount of lab preparation and time spent determining results, giving a food processor more control and improving food safety.