Enhanced survival of Campylobacter jejuni in association with wood

Campylobacter jejuni cells, when stressed by aeration of the liquid culture medium, were protected from death when a block of wood was present in the broth, especially at 30 degrees C. Sealing the wood inside a porous membrane showed that access to its physical structure was necessary for the protection of cells and that soluble free-radical scavengers from the wood were not responsible for the protection seen. Insoluble free-radical scavengers associated with the wood were not a significant factor since other porous materials offered protection when their pores were sufficiently small (around 16 mu m); and the wood itself needed to be at least 4 mm thick for the effect to be evident. Deeply scored plastic blocks did not enhance the survival of cells in aerated broths. Scanning electron microscopy was used to determine the size of the openings within the wood in relation to the size of the bacterial cells. Thus it was established that the physical structure of the wood, rather than its chemistry, was responsible for its protective effect. The consequences of this finding for the use of wooden cutting boards in food handling are discussed.