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May/June 2008

Development of Latest Proposed Biofilm Standard Launched

ASTM International Committee E35 on Pesticides and Alternative Control Agents has begun work on the latest in a series of standards on biofilm. The proposed new standard, WK17813, Quantification of a Pseudomonas aeruginosa Biofilm Grown with Low Shear and Continuous Flow Using a Drip Flow Biofilm Reactor, is being developed by Subcommittee E35.15 on Antimicrobial Agents.

Drip Flow Biofilm Reactor

Drip Flow Biofilm Reactor

According to Darla M. Goeres, senior research engineer, Center for Biofilm Engineering, and an E35 member, biofilm is defined as microorganisms living in a self-organized cooperative community. These communities, which are embedded in slime and can be found on a variety of surfaces, can have positive and negative effects and are currently being investigated by industry, medical, professional and regulatory agencies.

Goeres says that the qualitative characteristics that define a particular biofilm, such as architecture, population density, microbial ecology and chemical composition, are controlled by the physiochemical properties of the environment where the biofilm exists.

“Intuitively, the biofilm found in a chronic wound infection is different than the biofilm found in drinking water distribution systems or the biofilm present in constructed wetlands,” says Goeres. “Laboratory biofilms are engineered to exhibit a particular set of qualitative characteristics that best represent the environment under investigation.”

WK17813 describes how to grow a repeatable Pseudomonas aeruginosa biofilm using the drip flow biofilm reactor. The difference between biofilm grown with this type of reactor and those covered in previous biofilm standards (E2562, Test Method for Quantification of Pseudomonas aeruginosa Biofilm Grown with High Shear and Continuous Flow Using CDC Biofilm Reactor; and E2196, Test Method for Quantification of a Pseudomonas aeruginosa Biofilm Grown with Shear and Continuous Flow Using a Rotating Disk Reactor) is that biofilm is grown under low fluid shear close to the air/liquid interface and that the drip flow reactor is a plug flow reactor system, resulting in biofilm that is visible to the naked eye and smooth and slimy in appearance. Biofilm generated in a drip flow reactor could represent those found in a wide spectrum of places, including cooling towers, produce sprayers, on food processing conveyor belts, on catheters and in lungs with cystic fibrosis.

“Like any other engineering field, when growing a biofilm in the laboratory, it is important to have the best tool for the job at hand, meaning that biofilm researchers will need a collection of laboratory reactors that grow different types of biofilm,” notes Goeres. Interested parties are invited to join the ongoing standards developing activities of Subcommittee E35.15.


Technical Information: Darla M. Goeres, Center for Biofilm Engineering, Montana State University

Phone: 406/994-2440

ASTM Staff: Jennifer Rodgers

Phone: 610/832-9694