This semi-quantitative method of AOAC International is to test disinfectant-soaked towelettes for decontamination of environmental surfaces. The data generated can be submitted to the U.S. Environmental Protection Agency (EPA) and Health Canada. The method recommends the use of Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica as the test organisms. However, other types of bacteria and fungi of clinical, occupational or domestic relevance may also be tested using appropriate culture and viability assay procedures.

The protocol is designed to test towelettes impregnated or pre-saturated with a test substance to sequentially wipe glass slides (“carriers”) with dried inocula on them. At the end of the contact time, the carriers are  individually placed in tubes a liquid recovery medium with a neutralizer. The tubes are incubated and visually examined for the presence or absence of turbidity.
The main steps in this semi-quantitative method are summarized in the flowchart below.
For product registration, three production lots must be tested against each one of the three organisms.

GSPT has the following limitations:
– Semi-quantitative
– Operator- and technique-sensitivity may yield variable results
– Inoculum drying conditions not properly specified
– The surface of glass slides not representative of many environmental surfaces
– Unsuitable for testing virucidal activity