Antimicrobial Activity in Aqueous and Methanolic Leaf Extract of Eupatorium odoratum against Bacteria of Clinical and Nonclinical Origin

Abstract

Eupatorium odoratum is an invasive weed in most parts of the world. Though toxic to human and animals its leaf juice has been indicated for application on fresh wounds. In the study Eupatorium odoratum methanolic extract (EOME) and crushed leaf extract (EOE) from fresh leaves were tested for antimicrobial activity against 893 strains belonging to more than 140 species of 40 genera. The EOME inhibited 31.9% and EOE inhibited only 5.36% strains. There was no significant ( p >0.05) correlation ( r, -0.02) between antimicrobial activity of EOE and EOME. Instead, strong ( p , 0.01) positive correlation ( r, 0.245) was evident between sensitivity of strains to EOME and tetracycline. More of the Bacillus, Brucella and Burhkolderia spp.strains were sensitive to EOME than strains of other bacteria. Pasteurellamultocida type B ( p, 0.01) and Salmonellaindica ( p, 0.009) strains were more frequently sensitive to EOME than strains of other species of the respective genera. Among bacterial strains of different origin sensitivity to EOME ranged from 12.5% to 50.4%. Bacteria of food (Axone) origin (50.4%) were more frequently sensitive to EOME than reference strains ( p, 0.002) and strains of pig ( p <0.001), cattle ( p, 0.001), human ( p, 0.009), horse ( p, 0.049), wall lizard ( p <0.001), environment ( p, 0.007) and zoo animal ( p< 0.001) origin. There was no difference in sensitivity to EOME in strains isolated from biotic and abiotic environment ( p, 0.11) irrespective of their G+ve ( p, 0.16) or G-ve ( p, 0.42) trait. Significantly more ( p, 0.046) number of bacteria of environmental origin were sensitive to EOME than those isolated from animal sources. Of the 287 G+ve and 579 G-ve bacterial strains tested, G+ve bacteria were more frequently ( p <0.001) sensitive (87.5%) to tetracycline than G-ve bacterial (69.61) strains. Source of G+ bacteria had no significant ( p, 0.4) bearing on their sensitivity to tetracycline (TetS). However, G-ve bacteria isolated from Axone were more commonly TetS type than strains of environmental (0.003) and animal origin ( p, 0.024) especially those associated with illness ( p, 0.036) and mortality ( p, 0.008). The study concluded that crushed leaf extract of E. odoratum (EOE) though effective on many of the bacteria associated with wound infection, was less effective antimicrobial than methanolic extract of the herb (EOME). There was good correlation between sensitivity of bacterial strains to tetracycline and EOME. Markedly good antibacterial activity of EOME on some of the important pathogens of animals including Brucella, Pasteurella and Burkholderia spp. indicated that the herb may be a potential source of useful antimicrobial component(s).