Both ISO 11930 and USP <51> require testing against five organisms: Staphylococcus aureus (gram-positive bacterium), Escherichia coli (gram-negative bacterium), Pseudomonas aeruginosa (gram-negative bacterium), Candida albicans (yeast), and Aspergillus brasiliensis (mould). Some labs or buyers request additional organisms for specific product types, such as Burkholderia cepacia for high-risk rinse-off products.
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