ASTM E3161-21 PDF

SIGNIFICANCE AND USE 5.1 Bacteria that exist in biofilms are phenotypically different from suspended cells of the same genotype. Research has shown that biofilm bacteria are more difficult to kill than suspended bacteria (4, 5). Laboratory biofilms are engineered in growth reactors designed to produce a specific biofilm type. Altering system parameters will correspondingly result in a change in the biofilm. The purpose of this practice is to direct a user in the growth of a P. aeruginosa or S. aureus biofilm by clearly defining the operational parameters to grow a biofilm that can be assessed for efficacy using the Standard Test Method for Evaluating Disinfectant Efficacy Against Pseudomonas aeruginosa Biofilm Grown in CDC Biofilm Reactor Using Single Tube Method (E2871). 5.2 Operating the CDC Biofilm Reactor at the conditions specified in this method generates biofilm at log densities (log10 CFU per coupon) ranging from 8.0 to 9.5 for P. aeruginosa and 7.5 to 9.0 for S. aureus. These levels of biofilm are anticipated on surfaces conducive to biofilm formation such as the conditions outlined in this method. 5.2.1 To achieve an S. aureus biofilm with a population comparable to that for P. aeruginosa using the bacterial liquid growth medium conditions specified here, the S. aureus biofilm must be grown at 36 °C ±2 °C rather than at room temperature (21 °C ±2 °C). SCOPE 1.1 This practice specifies the parameters for growing a Pseudomonas aeruginosa (ATCC 15442) or Staphylococcus aureus (ATCC 6538) biofilm that can be used for disinfectant efficacy testing using the Test Method for Evaluating Disinfectant Efficacy Against Pseudomonas aeruginosa Biofilm Grown in CDC Biofilm Reactor Using Single Tube Method (E2871) or in an alternate method capable of accommodating the coupons used in the CDC Biofilm Reactor. The resulting biofilm is representative of generalized situations where biofilm exist on hard, non-porous surfaces under shear rather than being representative of one particular environment. Additional bacteria may be grown using the basic procedure outlined in this document, however, alternative preparation procedures for frozen stock cultures and biofilm generation (for example, medium concentrations, baffle speed, temperature, incubation times, coupon types, etc.) may be necessary. 1.2 This practice uses the CDC Biofilm Reactor created by the Centers for Disease Control and Prevention (1).2 The CDC Biofilm Reactor is a continuously stirred tank reactor (CSTR) with high wall shear. The reactor is versatile and may also be used for growing or characterizing various species of biofilm, or both (2-4) provided appropriate adjustments are made to the growth media and operational parameters of the reactor. 1.3 Basic microbiology training is required to perform this practice. 1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this practice. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.