Quantitative test for bacteria

Two widely used tests to evaluate plastics or similar materials (polymeric fibers) measure the percent reduction or percent survival of bacterial cells over a 24-hour period. The tests are  

The procedures allow the biologist to inoculate the test samples with a known amount of viable bacterial cells of about 10 organisms or CFU (cell forming units) in the inoculum. 

Other organisms can be used by agreement of the interested parties and appropriate to the end use applications. The samples are inoculated, and then incubated for 24 hours. Following standard microbiological techniques (plate count), the surviving organisms are recovered and the percent reduction is calculated. 

The AATCC Method does not specify a pass/fail criterion. Interested parties or industrial trade groups and organizations may set up their own criteria. The NYS 63 has passing criteria of 2% survival for Staphylococcus aureus and 17% survival of Klebsiella pneumoniae. 

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