Please explain this expression, thanks:?

I am reading about a serum and I don’t understand the expression in capital letters in the following paragraph. Please, explain this expression to me. Thanks: “Quality control All batches of the product are subjected to performance and sterility tests, the microorganisms used in the performance assay, are PART OF... show more I am reading about a serum and I don’t understand the expression in capital letters in the following paragraph. Please, explain this expression to me. Thanks:

“Quality control

All batches of the product are subjected to performance and sterility tests, the microorganisms used in the performance assay, are PART OF OUR ATCC STANDARDS AND CLINICAL ISOLATES”
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