The use of wood in practice - A hygienic risk?

The survival of bacteria on wood was investigated in laboratory experiments using naturally occurring and hygienically relevant bacteria and in a trial performed in a meat factory. Different types of wood dust (pine, larch, maple) and polyethylene chips were inoculated with chicken manure to study the interactions of bacteria and wood. The survival of the different bacteria from chicken manure was followed by plating on selective media. In addition, denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments from directly extracted DNA was used to precisely analyze changes in the relative abundance and composition of the manure-derived bacterial community on wood and plastic. Bands of DGGE-community profiles which reflected changes in the composition of the bacterial community on wood and plastic were excised, re-amplified, cloned and analyzed by sequencing. A rapid decrease of CFU of manure-derived bacteria was observed on pine-wood which correlated with the decreased amount of DNA extracted from pine-wood. Bacteria applied on larch, maple and plastic survived longer than on pine. Investigations have shown that some bacterial groups, e.g. enterobacteria, are more affected by wood and plastic than other bacteria. Furthermore, our results indicated that extractives from different wood types influenced the survival of bacterial species differently. Better hygienic characteristics of pine-wood compared to plastic as a material for transportation pallets were also observed in preliminary tests under practice conditions during a 4-week test in a meat processing factory.