Antimicrobial Activity of Isolated Bacterial Endophytes from Cichorium intybus L, Pelargonium hortorum, and Portulaca oleracea Against Human Nosocomial Bacterial Pathogens

Abstract

Background: Bacterial endophytes are colonizers of the inner plant tissues in which they do not normally cause any substantial morphological changes or disease symptoms. Endophytic bacteria are safe microorganisms that reside within the plant hosts and are known to enhance the growth and development of host plants, probably by secreting growth hormones. These bacteria are known to enhance growth and products of plants by fixing atmospheric nitrogen, solubilization of phosphate, production of phytohormones and siderophores, and possession of antagonistic activity, as well as reducing the level of stress ethylene in host plants. Objectives:In this descriptive study, we focused on the isolation of bacterial endophytes from three medicinal plants Cichorium intybus L, Pelargonium hortorum, and Portulaca oleracea and screened them for activities against nosocomial isolates of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeroginosa, and Acinetobacter baumannii. Methods: Random samples from asymptomatic leaves and branches of three medicinal plants (Cichorium intybus L, Pelargonium hortorum, and Portulaca oleracea) were collected. To isolate the endophytic bacteria, the disinfected portions of the plants were distributed onto the isolation media. To examine endophytic bacterial contents, bioassays were conducted using growing colonies in PA and YEA, inactivating them by chloroform. To test the antibacterial activity of the endophytic bacterial culture broth, filtersterilized supernatants were poured into cylinders on each bacterial plate. Results: A total of 24 phenotypically distinguishable bacterial endophytes were isolated in pure form from three medicinal plants. In part of the chloroform-inactivated colonies of all 24 isolated endophytes, the most effective herb was C. intybus L, followed by Po. oleracea, and in part of the supernatant culture broth, the most effective herb was Po. oleracea, followed by C. intybus L. Conclusions: Endophytic microorganisms residing in Cichorium intybus L, Portulaca oleracea, and Pelargonium hortorum are a very promising source for production of bioactive compounds. In general, most isolated endophytes had an acceptable effect against indicator bacterial pathogens.