The Antibacterial Activity of Secondary Metabolites of EndophyticBacterial Isolates of Carica Papaya against Some Clinical Isolates

Plants which are used in traditional medicines are of significant importance and therefore considerableresearch has been carried out on medicinal plants for bioactive compounds. However, limited researchhas been performed on the associated microorganisms, especially bacterial endophytes which couldserve a good source of novel antibiotic agents. This study was aimed to determine the antibacterialactivity of secondary metabolites of endophytic bacterial isolates of Carica papaya plant parts againstsome clinical isolates. Clinical isolates used in this study were Escherichia coli, Klebsilla species,Staphylococcus aureus, and Salmonella species. Endophytes were cultured, isolated and identifiedusing morphological and biochemical tests and five endophytes were isolated and observed to be Gramnegative rod. The endophytes were presumed to be flavobacterium species and Pseudomonas species.Endophtic bacterial isolates were further confirmed using molecular method. The confirmed bacteriastrains were Myroides odoratimimus from Carica papaya leaf, and Empedobacter brevis from Caricapapaya root and stem. Isolated endophytes were sub-cultured in nutrient broth and secondarymetabolites were extracted from the medium using Ethyl acetate. Crude extracts of secondarymetabolites were then subjected to Liquid Chromatography and Mass spectrometry (LCMS) whereLupinine, pyridine, Aniline, Polyketides and Cyanopyridine where the most prevalent metabolitesdetected in the three ethyl acetate secondary metabolite extracts of bacterial endophytes analysed. Thecrude extracts were tested against the test isolates for antibacterial activity and result shows that all thesecondary metabolite had activity against at least two out of the four clinical isolates used in this studywith zones of inhibition ranging from 9mm to 22mm. The zones of inhibition observed indicates thatthe secondary metabolites extracted from bacterial endophytes of Carica papaya leaf, stem and roothave antibacterial activities and as such can be explored as good sources of antibacterial agents for thedevelopment of therapeutic drugs.Key words: Antibacterial, Bacterial endophytes, Clinical isolates, Secondary metabolite