Effect of volatile organic compounds from Pinus sylvestris and Picea abies on Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae and Salmonella enterica serovar Typhimurium

Pine and spruce heartwood and sapwood were milled to wood particles and the volatile organic compounds (VOCs) of the wood particles were tested against four bacterial strains. To study the influence of relative humidity on the antibacterial effect, both dry and wet wood particles were tested. Twenty microliters of the bacterial dilution with a concentration of 1.5×10⁷ CFU ml^-1 was cultured on glass surfaces in the presence of VOCs and the amount of viable bacteria was studied after 2, 4, and 24 h. The volatile emissions were evaluated by GC/MS and the results were compared with the results from the bacterial trial. VOCs had an antibacterial effect on Escherichia coli, Streptococcus pneumoniae and slightly on Salmonella enterica serovar Typhimurium. But the effect on Staphylococcus aureus was minute even after 3 days' incubation. The dry wood particles generally had a stronger antibacterial effect, though the amount of VOCs from the wet wood was higher. Pine heartwood had the strongest antibacterial effect and also the highest emissions of VOCs. However, the interaction between different bacterial strains and wood species shows some variations.