Antibacterial activity of Acanthus sennii extracts against Staphylococcus aureus and Escherichia coli pathogens

Medicinal plants offer a major and accessible source of health care to people living in developing countries. Increasing drug resistant microbial infections intensified the search for new, safer, and more efficacious agents against microbial infections. Acanthus sennii is one of the medicinal plants used traditionally for the treatment of different infectious diseases in Ethiopia. Therefore, this study was carried out to evaluate antibacterial activity of A. sennii against pathogenic bacteria. Plant materials were extracted by maceration technique with chloroform, ethanol and water solvents. The antibacterial activities of the crude extracts of the plant were carried out by the agar well diffusion method. Broth dilution method was used to determine minimum inhibitory and streak plate bactericidal concentration of extracts. The results revealed that ethanol extracts of leaves revealed high antibacterial activity against standard strains of Staphylococcus aureus with inhibition zone of 14±0.6 mm at 25 mg/ml and 17±0.7 mm at 50 mg/ml. Ethanol extracts of buds showed high antibacterial activity against standard strains of S. aureus with inhibition zone of 25.7±0.7 mm at 100 mg/ml, also against standard strains of E. coli with inhibition zone of 16 mm at 50 mg/ml and 23.7 mm at 100 mg/ml. The mean minimum inhibitory concentration of 5.2±1.8 and 2.6±0.5 mg/ml was recorded for ethanol extract of leaves against standard strains of E. coli and clinical isolates of S. aureus; the mean minimum bactericidal concentration of 4.2±1.0 mg/ml with ethanol extract of leaves against standard strains of S. aureus; and the mean minimum bactericidal concentration of 12.5 mg/ml against standard strains and clinical isolates of E. coli. The result showed that A. sennii could be a candidate in the search for new antibacterial agents against these bacteria and its use in ethnomedicinal treatment of infectious diseases used by local communities may be validated. Isolating bio-active components and determining toxicity are future agenda. Keywords: Acanthus sennii, Antibacterial activity, E. coli, Minimum inhibition concentration, Minimum bactericidal concentration, S. aureus