ASTM E2871-12

Vegetative biofilm bacteria are phenotypically different from suspended planktonic cells of the same genotype. Biofilm growth reactors are engineered to produce biofilms with specific characteristics (2). Altering either the engineered system or operating conditions will modify those characteristics as well as the physicochemical environment. The goal in biofilm research and efficacy testing is to choose the growth reactor and operating conditions that generate the most relevant biofilm for the particular study.

The test method was developed using Pseudomonas aeruginosa ATCC 15442 biofilm grown on borosilicate glass coupons in the CDC Biofilm Reactor and liquid disinfectants. Efficacy data developed using other bacteria, different shear, different coupons, or other standardized biofilm reactor systems, and/or other forms of disinfectants may result in different log₁₀ reduction (LR) values and repeatability and reproducibility standard deviations.

The efficacy test was designed to determine the log₁₀ reduction in bacteria after exposure to a disinfectant in a closed system.

The test method was developed using 50-mL conical tubes. The conical geometry allows for disinfectant exposure to biofilm on all surfaces of the coupon.

Each efficacy test includes a single contact time and temperature for three untreated control coupons (exposed to buffered dilution water) and three treated coupons (per disinfectant/concentration combination).

1.1 This test method specifies the operational parameters required to perform a quantitative liquid disinfectant efficacy test against biofilm bacteria.

1.2 The test method was developed using a Pseudomonas aeruginosa biofilm grown in the CDC Biofilm Reactor (Test Method E2562), modified to include borosilicate glass coupons as a hard nonporous surface and P. aeruginosa ATCC 15442.

1.3 Disinfectant preparation and contact time are used in the assessment according to the manufacturer’s instructions for use.

1.4 The test method uses a closed system to treat biofilm. A coupon is placed in a single tube for the treatment, neutralization, and sampling steps to prevent the loss of cells.

1.5 Verification of disinfectant neutralization is determined prior to conducting the test method.

1.6 This test method describes how to sample and analyze treated and untreated control biofilms for viable cells. Biofilm population density is recorded as log₁₀ colony-forming units per coupon. Efficacy is reported as a log₁₀ reduction of viable cells.

1.7 Basic microbiology training is required to perform this assay.

1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.9 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 and health practices and determine the applicability of regulatory limitations prior to use.