Bioburden Testing Procedures and Tips

The Bioburden Testing Procedure

Our Bioburden testing is conducted according to ISO 11737 and includes validation procedures. Before conducting Bioburden Testing, validation is performed.

Validation procedures consist of assessment of the adequacy of the extraction techniques to remove microorganisms (Recovery Efficiency), the calculation of a correction factor based on the recovery efficiency and assessment of the adequacy of the culture conditions to optimize the count obtained.

Nova’s Experience With Both Validation Techniques

  • Validation using inoculated product
  • Validation using repetitive recovery or exhaustive recovery

Validation methods should be indicated on the chain of custody when submitting samples. Otherwise, Nova will select the validation method for the product.

Our methods for the determination of Bioburden are also performed by ISO 11737 standards. Our methods for removal of microorganisms include both elution techniques as well as non-elution techniques.

*Removal techniques should be indicated on the chain of custody when submitting samples. Otherwise, Nova will select the removal technique for the product.

Removal Techniques By Elution

  • Stomaching
  • Ultrasonication
  • Shaking
  • Vortex Mixing
  • Flushing
  • Blending
  • Swabbing

Nova’s SOP for Bioburden testing utilizes membrane filtration of the eluent, followed by incubation of the filter in an appropriate growth medium to give visible colonies. Membrane filtration is particularly useful for products with a low bioburden and for products that contain microbiocidal or microbiostatic substances.

Removal Techniques By Non-Elution

  • Contact Plating
  • Agar Overlay
  • Most Probable Number (MPN)

Our incubation and enumeration techniques for Bioburden testing are also performed by ISO 117371 standards. Following incubation, our enumeration techniques include:


  • Total Aerobic Count
  • Spore Forming Colony Count
  • TotaYeastst and Mold Count

*If other techniques such as pour plating, spread plating, or spiral plating are desired; it should be indicated on the chain of custody when submitting samples.

Tips for Selecting Product for Bioburden Testing

  • It is common practice to use a sample size of between 3 to 10 items for routine monitoring of bioburden levels.
  • The first prerequisite is that product selected should possess bioburden representative of that of product.
  • When selecting and handling samples avoid significantly altering the numbers and types of microorganisms that are inherent in manufacturing of that product.
  • In choosing samples of product for determination of bioburden, there are two possibilities:
    • Take product at random OR
    • Take product that is not suitable for sale, which may be scrapped or otherwise rejected.
  • If the decision is made to utilize a rejected product, such product should have undergone all essential stages of production, including possible cleaning and packaging processes.
  • Product taken at random is in general, the more desirable sample.
  • Selection of products for Bioburden testing should be consistent to allow comparisons of bioburden to be made over a period of time.
  • When sampling for determination of bioburden, product should be contained in its usual packaging.
  • If data from bioburden determinations are to be used to establish a sterilization process, the period of time that elapses between the selection of product samples and the determination of bioburden should reflect the time period between completion of the last manufacturing step and sterilization of product.
  • The frequency of monitoring should take into account a variety of factors that include the following. (Sampling may be performed at a frequency based on time or production volume.)
    • Availability of historical data
    • Purpose for generating the data
    • Nature of the manufacturing process
    • Production frequency for the product
    • Criticality of detecting bioburden changes in a timely fashion
    • Seasonal and environmental variations
  • In order to establish baseline levels, it is common practice to determine bioburden at a higher frequency during the initial production of a new product and for this frequency to be reduced as a knowledge of bioburden develops.
  • The frequency of determinations of bioburden should allow detection of changes in bioburden, for example, due to seasonal variations, manufacturing changes or changes in materials.

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