Preliminary Evaluations of the Antibacterial Activity of Tasmannia lanceolata against Bacillus anthracis: Natural Resource Probing to Prevent Anthrax

Introduction: Bacillus anthracis is bacterial cause of the highly fatal, zoonotic disease anthrax. Tasmanian pepper (Tasmannia lanceolata) has been previously documented for its antiseptic properties against other pathogenic bacteria. This study sought to investigate the effectiveness of T. lanceolata as an inhibitory agent against B. anthracis. Methods: Tasmannia lanceolata berry and leaf extracts were prepared with either water or methanol as the extraction solvent. Growth inhibition was assessed against B. anthracis strain PMO through disc diffusion as assaying. The relative MIC values of each extract was quantified to evaluate efficacy as a sterilant. The degree of toxicity of each extract was achieved using the widely used Artemia franciscana nauplii bioassay. Results: T. lanceolata leaf extracts inhibited the growth of B. anthracis in the disc diffusion assay, with MIC values of 2333 and 1873 μg/mL respectively. In contrast, the T. lanceolata berry extracts were completely devoid of growth inhibitory activity. All T. lanceolata extracts (both berry and leaf) were non-toxic (LC₅₀ values substantially >1000 μg/mL) as determined via the Artemia franciscana bioassay. Conclusion: T. lanceolata berry and leaf extracts are not only non-toxicity, but also had moderate growth inhibitory bioactivity against B. anthracis, highlighting their potential in the treatment of anthrax.