Troubleshooting for antimicrobial finishes

A general problem of antimicrobial finishes is their selective effect. Some are 

Procedure Similar to AATCC TM 147 (Table 15.1) and ISO 20645. Agar may contain a nutrient or be nutrient-free to test if samples are a viable carbon source. Samples are buried up to 28 days, longer for coatings and plastics. Samples are sprayed with a mixed spore suspension (fungi) and held over water. Organism must obtain its carbon from material under test. Inoculated samples are left in contact for 0-24 hour. Organisms are then extracted and counted. 

Evaluation Visual, growth of contact and halo Loss of tensile strength or weight. Control samples must rot in about 7 days. Visual assessment (including a microscope) Number of colony forming units (cfu) 

Advantages Quick test for bacteria and fungi, variability of test conditions The most severe test Especially suitable for testing fungi or yeasts Relatively quick, distinguishes between biocide and biostat 

Disadvantages Size of halo indicates high diffusion or efficiency of the biocide Long term and expensive Long time of incubation Only for bacteria. Time consuming and expensive 

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