In vivo assessment of antibacterial activity of Cassia sieberiana stem bark extracts on enterohaemorrhagic Escherichia coli infection in Wister rats

Abstract

Background: The acceptance of traditional medicine as an alternative form of health care has led researchers to further investigate the antimicrobial and other health benefits of medicinal plants including Cassia sieberiana. The objective of this study is to assess the in vivo antibacterial effects of C. sieberiana stem bark extracts on infections caused by human and animal isolates of enterohaemorrhagic Escherichia coli (EHEC) in Wister rats. Methodology: This in vivo study was designed for 21 days in 3 phases of 7 days each; adaptation, infection and treatment. Escherichia coli were isolated from aerobic cultures of human and cattle faecal samples and EHEC 0157 identified by serological typing using latex agglutination method. Aqueous and ethanol extracts of authenticated C. sieberiana stem bark, were prepared using standard method. Forty-five Wister rats were randomly divided into 9 groups (A-I) of 5 rats each. Rats in group A (uninfected with human or animal EHEC isolate and untreated) served as negative control  while rats in group B (infected with EHEC animal isolate and untreated) and group C (infected with EHEC human isolate and untreated) served as  positive controls. Rats in group C through group I were experimental groups that were either infected with human or animal EHEC isolate and  treated, or uninfected but treated with ethanol and aqueous extracts of C. sieberiana. During each of the study phase, faecal samples were collected  from the rats and processed for evaluation of EHEC count and to determine faecal occult blood. Data were analyzed using the Statistical Package for  Social Sciences, version 20.0 and categorical variables were compared with Pearson’s Chi-square, with significant value taken as p<0.05 Results: Three EHEC isolates (2 from cattle and 1 from human) were identified from 22 E. coli isolates cultured from cattle and human faecal  samples. Rats in group A (negative control) and those in group G (infected with EHEC human isolate and treated with ethanol extract), group H (not  infected but treated with aqueous extract) and group I (not infected but treated with ethanol extract) were faecal occult blood negative throughout  the study period. Rats in group B (infected with animal isolate of EHEC without treatment) were occult blood negative after infection on day 14 but  positive on day 21, while rats in group C (infected with human isolate of EHEC without treatment) were occult blood positive on day 14 but negative  on day 21. Rats in groups D, E and F infected with human and cattle EHEC isolates and treated, were faecal occult blood positive on day 14 but  negative on day 21, with high colony counts recorded, cleared within 7 days of treatment by both aqueous and ethanolic extracts of C. sieberiana.   Conclusion: The findings of this study confirmed the antibacterial potentials of C. sieberiana stem bark against EHEC. The beneficial effects of this plant extract should be exploited for commercial medicinal purposes.