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 (5, 7). 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. For example, research has shown that biofilm grown under high shear is more difficult to kill than biofilm grown under low shear (5, 8). The purpose of this test method is to direct a user in the laboratory study of a Pseudomonas aeruginosa biofilm by clearly defining each system parameter. This test method will enable an investigator to grow, sample, and analyze a Pseudomonas aeruginosa biofilm grown under high shear. The biofilm generated in the CDC Biofilm Reactor is also suitable for efficacy testing. After the 48 h growth phase is complete, the user may add the treatment in situ or harvest the coupons and treat them individually.
1.1 This test method specifies the operational parameters required to grow a reproducible (1) Pseudomonas aeruginosa biofilm under high shear. The resulting biofilm is representative of generalized situations where biofilm exists under high shear rather than being representative of one particular environment.
1.2 This test method uses the Centers for Disease Control and Prevention (CDC) Biofilm Reactor. The CDC Biofilm Reactor is a continuously stirred tank reactor (CSTR) with high wall shear. Although it was originally designed to model a potable water system for the evaluation of Legionella pneumophila (2), the reactor is versatile and may also be used for growing and/or characterizing biofilm of varying species (3-5).
1.3 This test method describes how to sample and analyze biofilm for viable cells. Biofilm population density is recorded as log10 colony forming units per surface area.
1.4 Basic microbiology training is required to perform this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
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