Screening for In vitro antibacterial activity of leaves extracts of certain selected plants against Rhodococcus equi

In the present study, the research work was carried out during June 2018 to March 2019 at ICAR-NRCE-EPC (Indian Council of Agricultural Research, National Research Centre on Equines, Equine Production Campus), Jorbeer, Bikaner (Rajasthan), India. The study was conducted to investigate in vitro antibacterial activity of ethanolic, chloroformic and Sequentially Extracted Water Extract (SEWE) leaves extracts of Aegle marmelos, Morus alba, Nerium indicum, Cascabela thevetia (L.) Lippold, Plumeria alba L. and Azadirachta indica against Vap A and Vap C positive Rhodococcus equi. Fresh leaves of these plants were collected manually from campus of ICAR-NRCE-EPC, Jorbeer, Bikaner (Rajasthan). In initial screening ethanolic leaves extract of these plants except Azadirachta indica, were found non-active against Rhodococcus equi. Chloroformic leaves extracts of Azadirachta indica did not showed in vitro antibacterial activity against Rhodococcus equi. While ethanolic and Sequentially Extracted Water Extract (SEWE) leaves extracts of Azadirachta indica showed good in vitro antibacterial activity against Rhodococcus equi. Further, solvent based fractionation, Ethanol Soluble Fraction (ESF), Methanol Soluble Fraction (MSF) and Water Soluble Fraction (WSF) of polar compounds of SEWE did not showed in vitro antibacterial activity against Rhodococcus equi. On comparison with currently used antibiotics (azithromycin and rifampicin), required concentration of the leaves extract of Azadirachta indica was too high for their possibilities of in vivo use, so abundant availability of Azadirachta indica leaves and their activity against Rhodococcus equi suggests their potential for use as disinfectant against Rhodococcus equi.