Antimicrobial Activity of Methanolic Extract and Ether Extract of Ageratum conyzoides

Abstract

Ageratum conyzoides, a weed prevalent in India, is known for its several therapeutic uses to control infections. In the present study we compared the antimicrobial potential of its ether extract and methanolic extract with ciprofloxacin on 294 strains of Gram positive bacteria (GPBs), 575 strains of Gram negative bacteria (GNBs), 15 yeast and 5 mould strains of clinical and nonclinical origin belonging to 49 genera and more than 155 species using disc diffusion assay. The microbial strains in the study were isolated from samples of abiotic (41) and biotic (101) environment, foods (81), clinically sick (441), dead (108) and healthy (75) animals and human beings, and 42 were reference strains. The study revealed that there was no appreciable difference in antimicrobial activity of ether extract (ACEE) or methanolic extract (ACME) of A. conyzoides. A total of 214 (24.1%) strains were sensitive to ACME while of the 697 strains tested for ciprofloxacin 551 (79.1%) were sensitive. Sensitivity to ACME among 294 GPBs (44.9%) was significantly (p<0.0001) higher than among 575 strains of GNBs (12.4%). There was no significant difference among GPBs and GNBs for ciprofloxacin (one of the most commonly used antibiotics in India) sensitivity, but oxidase negative GNBs (385) as well as GPBs (238) were about two times more commonly sensitive to ciprofloxacin than 190 oxidase positive GNBs (p = 0.001) and 56 oxidase positive GPBs (p, 0.03), respectively. For ACME oxidase positive strains had 2.4 times more odds (p < 0.0001) in their favour of being sensitive to ACME (53.4%) than oxidase negative strains (18.6%). The most sensitive strains to ACME belonged to oxidase positive GPBs (62.5%) followed by oxidase negative GPBs (40.8%), oxidase positive GNBs (27.4%) and oxidase negative GNBs (4.9%). All Aeromonas, Alcaligenes, Klebsiella, and Proteus species strains were resistant to ACME irrespective of source of isolation or association with illness. In contrast, majority of the strains of Burkholderia (76.9%), Bacillus (66.7%) and Brucella (53.8%) species were sensitive to ACME. The study revealed that A. conyzoides might be containing useful antimicrobial component(s) more active against oxidase positive potentially pathogenic strains often associated with systemic and deadly infections in animals as well as in humans.