Microbial bioburden tests are done according to USP<797>, <51>, <61>, <62>, and FDA cGMP guidances to assess the presence, numbers and types of microorganisms in association with sterilized final products, tissues, raw materials, procedures and other aspects of the processing environment. Culture plates, serial dilutions of materials and other methods are routinely applied, as appropriate for the material being tested. Types of bioburden testing include: aerobic, anaerobic, bacteria, fungi, and sporulating organisms. Microbial identification may be pursued by Gram stain, cell morphology, specialty stains, or outsourcing species molecular identification. Controls are included in validation of the test systems as are uninoculated controls in all bioburden tests.