Abstract
BackgroundAnthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive spore-forming bacterium. The presence of the bacteria and the toxins in the blood of infected hosts trigger a cascade of pathological events leading to death. Nine medicinal plants with good activities against other bacteria were selected to determine their in vitro antibacterial activity against Bacillus anthracis Sterne strain. The cytotoxicity of the extracts on Vero kidney cells was also determined.ResultsThe minimum inhibitory concentration (MIC) values of the extracts against Bacillus anthracis Sterne strain ranged from 0.02 to 0.31 mg/ml. Excellent MIC values were observed for the following plant species: Maesa lanceolata (0.02 mg/ml), Bolusanthus speciosus, Hypericum roeperianum, Morus mesozygia (0.04 mg/ml) and Pittosporum viridiflorum (0.08 mg/ml). The total antibacterial activity of the extracts ranged from 92 to 5562 ml/g. Total activity presents the volume to which the extract from 1 g of plant material can be diluted and still inhibit microbial growth. Maesa lanceolata and Hypericum roeperianum had the highest total activity with values of 5562 and 2999 ml/g respectively. The extracts of Calpurnia aurea had the lowest total activity (92 ml/g). The cytotoxicity determined on Vero cells indicated that most of the extracts were relatively non-toxic compared to doxorubicin (LC50 8.3 ± 1.76 μg/ml), except for the extracts of Maesa lanceolata, Elaeodendron croceum and Calpurnia aurea with LC50 values at 2.38 ± 0.25, 5.20 ± 0.24 and 13 ± 2.26 μg/ml respectively. The selectivity index (SI) ranged from 0.02 to 1.66. Hypericum roeperianum had the best selectivity index, (SI = 1.66) and Elaeodendron croceum had lowest value (SI = 0.02).ConclusionsThe crude acetone extracts of the selected plant species had promising antibacterial activity against Bacillus anthracis. Maesa lanceolata extracts could be useful as a disinfectant and Hypericum roeperianum could be useful to protect animals based on its high total activity and selectivity index. Further investigation of these plant extracts may lead to the development of new therapeutic agents to protect humans or animals against anthrax.
Highlights
Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive spore-forming bacterium
All the plant extracts tested against B. anthracis had promising activity (Table 2), their low extract yield affected the total activity values when compared to Maesa lanceolata and Hypericum roeperianum
Morus mesozygia, Bolusanthus speciosus, and Pittosporum viridiflorum had a lower total activity due to low extraction yield.The very low total activity of Calpurnia aurea can be ascribed to the high minimum inhibitory concentration (MIC) value and low Quantity extracted per 1 gram Mean MIC Total Activity Cytotoxicity selectivity index (SI)
Summary
Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive spore-forming bacterium. Anthrax is a serious zoonotic disease of great economic and social importance [1] It is caused by Bacillus anthracis, a Gram-positive spore-forming bacterium [2]. Elisha et al BMC Complementary and Alternative Medicine (2016) 16:5 toxin bearing plasmid pXO1 codes for three toxins, which cause haemorrhage, oedema, and necrosis [6] They comprise the lethal factor, oedema factor, and the protective antigen, in the host cell receptor component. The smaller capsule bearing plasmid pXO2 encodes three genes (cap B, cap C, and cap A) involved in the synthesis of the poly-D- glutamyl capsule that inhibits host phagocytosis of the vegetative form of B. anthracis. Microbiology laboratories use B. anthracis Sterne strain for accurate identification and diagnosis of anthrax, and occasionally for anthrax research [7]
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