In vitro screening of plant materials as anti-adhesive agents against E-coli K88

Due to the ban of antibiotics in feeds, alternative ways are needed to improve animal health and performance. A promising strategy is to supply animals with feed ingredients that act as alternative adhesion sites, thus facilitating bacterial shedding from the gut and reducing colonization and infection. In order to screen the ability of different materials as anti-adhesion agents, a microplate-based in vitro method was developed. In this test, different feed/food ingredients and plant by-products from the EU project Safewastes were tested for their binding ability towards the pig pathogen E. coli K88. ELISA microplates were coated with suspensions of powdered test ingredients in PBS buffer (Safewastes by-products SW1 to SW11, coffee grounds, konjac gum, locust bean gum, sesame seed expeller, tomato, yeast product) and incubated overnight at 4°C. Quenching was done with 1% BSA in PBS as blocking solution. BSA-coated wells were included as control. After lling with BHI broth, plates were incubated at 37°C in the reading chamber of a photometer. The O.D. was automatically read at a wavelength of 650 nm at 15 min intervals. All OD data were processed by non-linear regression analysis (P-NLIN, SAS). Parameters of the sigmoidal growth curves obtained were analysed by GLM procedure (SAS). The test principle was based on an inverse relationship between initial cell densities and the appearance of growth: The higher adhering cell numbers are, the shorter are the detection times of bacterial growth. Testing of different ingredients resulted in rankings according to their adhesive capacity towards E. coli K88, the sorting being based on the respective detection time of cell growth. Detection times ranged from 2.43 h (SEM=0.103 h) for the first position (yeast product) to 5.76 h (SW6) for the last one, being 4.47 h for BSA as a control. The yeast product, SW11, sesame seed expeller and SW7 had signicantly lower detection times with respect to control (P<0.05), and therefore were considered promising anti-adhesive agents against E. coli K88. These ingredients were destined for further testing and validation in an in vivo trial on challenged pigs.