Here are definitions of 'bioburden & bioburden testing':
"Bioburden is normally defined as the number of bacteria living on a surface that has not been sterilized"
"Bioburden testing is an assessment of the numbers and types of microorganisms present on a
product, and may be used for assessment of incoming materials, as an indicator of manufacturing
conditions, and to support sterilization validations. A determination of the recovery efficiency and
characterization (grouping micro-organisms into categories) are both required for compliance with
bioburden standards. All aspects of bioburden testing – test parameters, characterization and
recovery efficiency – are performed according to specified ISO, AAMI, USP, or FDA standards. "