Can manuka (Leptospermum scoparium) antimicrobial properties be utilised in the remediation of pathogen contaminated land?

Society is increasingly conscious of waste reduction and contaminant control. The application of biosolids to land (re-cycling) is one means of waste disposal that has been shown to improve various soil properties whilst re-using valuable nutrients. However, there is concern that land application of biosolids can introduce microbial contaminants to soil. The aim of this research was to investigate the potential use of manuka (Leptospermum scoparium), a shrub with known antimicrobial properties, to reduce microbial contaminants from land applied biosolids. We evaluated the efficacy of water extracted manuka components against five bacterial pathogens potentially found in biosolids. Water extracted manuka components significantly inhibited an Escherichia coli lux biosensor, as well as inhibited the growth of Salmonella typhimurium, E. coli 0157, Clostridium perfringins, Campylobacter jejuni and Listeria monocytogenes. EC50 calculations for these pathogens showed that 50% inhibition of growth occurred at relatively low manuka extract concentrations (0.07-27.9% v/v). For C. jejuni, complete inhibition of growth was observed at extract concentrations of 0.78%. These results indicate potential for the use of manuka in the rehabilitation of microbial contaminated sites.