Procedure At A Glance

For this method, sterile glass cover slips (carriers) are transferred into sterile petri plates then inoculated with 10 μl of the test bacteria. For products that only have a sanitizing/disinfecting claim, meaning a cleaning step to remove organic soil that precedes the sanitizing/disinfecting of the contaminated area, then the bacterial culture is used as is. For products with a cleaning and sanitizing/disinfecting claim then an organic soil is added to the bacterial culture to simulate blood, mucus, or dirt, etc. Inoculated carriers are dried for 30-40 minutes at 35 ± 2°C.  After the drying, the inoculated carriers are sprayed with the test product and held for a specified contact time. At the completion of the contact time, the treated carriers are transferred into neutralizing recovery medium. Testing is performed at ambient (room) temperature. The tubes are incubated for 48 hours at 35 ± 2°C and observed for growth (+) or no growth (-) of the test bacteria.

The control portion of the test method is to ensure validity of the testing being performed. Positive controls analyze the carriers after drying to measure the bacterial challenge exposed to the test substance. A valid test will have an average of >105 but less than 3.2 x 106 CFU/carrier for S. aureus and P. aeruginosa and an average of >104 but less than 3.2 x 105 CFU/carrier for S. enterica. Parallel controls mirror the test method without introducing an antimicrobial substance. This provides insight on how much bacteria are removed from the surface of the carriers by the spraying process. Carrier viability controls test whether or not the bacteria dried onto carriers can grow in the neutralizing medium. Media sterility controls ensure the test was performed with sterile medium to prevent contamination.

A neutralization control is included to ensure deactivation of the antibacterial chemistry in the test product at the conclusion of the contact time. This step is crucial in guaranteeing the validity of the test.

Typical test microorganisms include Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica.

Facility Expertise

Microchem Laboratory has been performing the AOAC Germicidal Spray Test for nearly twenty years. We have spent numerous hours perfecting in-house quality systems to ensure each method performed is done with the highest standard of excellence.  The AOAC Germicidal Spray Products Test can be modified for testing against fungi, viruses, tuberculocidal activity, and additional bacteria (i.e. MRSA, VRE, CRE)