Dr. Cliver, in a study by University of Wisconsin Madison, found that 99.9% of bacteria dies off within three minutes on wooden boards but none die on plastic ones! The study purposely contaminated the boards with Salmonella, Listeria and Escherichia coli that are common causes of food poisoning and were surprised to discover these results. The research was unable to identify the agents in wood that make it so inhospitable to bacteria.
They also found that when the boards were left unwashed overnight at room temperature, the bacterial counts increased on the plastic but none of the organisms could be recovered from the wooden boards the next morning.
Dr Clive still cautions chefs to not be sloppy and still wash off cutting surfaces after cutting meat, chicken or fish no matter the surface type (wood or plastic).
Also of note: the researchers used seven different species of trees and found similar results: wood was safer than plastic regardless of the materials used! Hurray!!!