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Title: Measurement of biofilm formation by Listeria species within a biofilm reactor

item Arnold, Judy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2006
Publication Date: 10/17/2006
Citation: Arnold, J.W. 2006. Measurement of biofilm formation by Listeria species within a biofilm reactor. p 101. . Meeting Abstract.

Interpretive Summary:

Technical Abstract: Health problems caused by foodborne illnesses that result from bacterial contamination have become a major concern for the public. Because of the severity of the illness, control of Listeria monocytogenes is a major concern for regulation and research. The present study monitored the growth of L. monocytogenes within a biofilm, a complex aggregation of microorganisms marked by the excretion of a protective and adhesive matrix. A biofilm reactor was used to grow the bacteria under flow conditions that mimic wet poultry processing and production areas. To determine the concentration of bacteria to add to the reactor for growth, the growth kinetics of each species was measured by spectrophotometry. The least significant difference test (P= 0.05) was used to determine differences among means of growth data from the six species of Listeria. Accordingly, the time of addition of each species was staggered over the first few hours for optimal compatibility in biofilm production. The reactor is equipped with a one-liter vessel that can maintain about 400 ml of bacterial suspension. A polyethylene top supports eight independent rods, which hold three removable coupons each. The coupons in the reactor were made of 304 stainless steel or glass. During operation, the coupons were under a consistent high shear from the rotation of a baffled stir bar. The flow rate of the reactor was adjusted to mimic food processing conditions and allow maximum biofilm growth on the surfaces of the coupons. The biofilm growth on a portion of coupons at the completion of each 24 h were scraped off, and placed into trypticase soy broth (TSB) at room temperature. The TSB with the biofilm was homogenized with a sterile CAT homogenizer. An aerobic plate count accounted for the initial presence of the bacteria in the reactor as well as on the coupons after 24 and 48 h. An equal portion of the coupons were stained with crystal violet dye, extracted with ethanol, and measured for biofilm production. All samples were performed in triplicate, and the experiments were replicated. The collected data will be used to grow stable biofilms of Listeria spp. for treatment with inhibitory compounds. An effective compound could be used for sanitation in food and health areas to help reduce cases of listeriosis across the nation.