In-vitro antibacterial activity of Annona senegalensis root and stem extracts against Salmonella typhimurium, Shigella flexneri and Escherichia coli

Abstract

The aim of the preset study was to determine the efficacy of Annona Senegalensis stem and root extracts against Salmonella typhimurium Shigella flexneri and Escherichia coli through the evaluation of bacterial sensitivity and determination of the minimum inhibitory and bactericidal concentration of the extracts against the test isolates. Plant materials were collected and duly authenticated. The methanoic and aqueous extracts prepared from the powdered forms were tested on the bacterial after cultural and biochemical identification of the isolates. The antibiotic sensitivity test was carried out using the Kirby Bauer disk diffusion method while chloramphenicol was used as the standard control. The Minimum Inhibitory Concentration (MIC) of the plant extracts were determined by broth dilution method while the Minimum Bactericidal Concentration (MBC) was determined by a method described using standard protocols. The ratio of MBC:MIC was computed to determine the bactericidal or bacteriostatic effects of the extracts. Data were analyzed using the Minitab 16 statistical package. Descriptive statistics (mean and standard error) and analysis of variance tools were applied while mean separation was done Fischer’s method at 5% level of significance. Antibacterial sensitivity test showed that the control test (Chloramphenicol) had significantly higher antibacterial sensitivity ( P<0.05) than any of the plant extract. Minimum Inhibitory Concentration (MIC) of the plant extract ranged from 6.25 mg/ml to 25.0 mg/ml. The lowest MIC of 6.25mg/ml was observed in Salmonella typhimurium among all extract types. Root and stem had similar effects on the test organisms (P>0.05) but, methanoic root extract had the lowest MBC of 6.25mg/ml against S.typhimurium and S. flexneri. Based on the MBC/MIC ratio, all extract types had bactericidal effects on Salmonella typhimurium and Shigella flexneri except aqueous root extract that showed bacteriostatic effect. Only the methanoic root and stem extracts exhibited bactericidal effects on Escherichia coli. Annona Senegalensis root and stem could possibly be explored commercially as an antibacterial agent against species of Salmonella, Shigellia and Escherichia.