Antibacterial potential of selected extracts and silver nanoparticles from bacterial endophyte harboured by Cola acuminata and Cola nitida (Sterculiaceae) roots

Abstract

IntroductionAntimicrobial resistance (AMR) is currently a global health issue in most countries. Harnessing endophytic at present. Antibiotic resistance occurs when bacteria can adapt and grow in the presence of antibiotics. Endophytic microorganisms as bio-factory of natural bioactive compounds, and their potential in nanotechnology remains largely under explored. The aim of this study was to evaluate the antibacterial activity of extracts and silver nanoparticles synthesised using bacterial endophytes isolated from Cola acuminata and Cola nitida roots. MethodologyThe roots of each plant were harvested, washed, cut and surface sterilised. The sterile pieces were placed on the surface of nutrient agar and incubated, after which the microorganisms were sub-cultured until pure colonies were obtained. Secondary metabolite production was then undertaken over a 12-day fermentation period in Mueller Hinton Broth, conducted under stringent aseptic conditions. Each microorganism was fermented in two different tanks. The first was used for the preparation of crude extracts, and the second for the synthesis of nanoparticles. The in vitro antibacterial activity was determined using the broth microdilution method against Pseudomonas aeruginosa, Proteus mirabilis, Acinetobacter sp. and Escherichia coli. The MIC and the time-kill kinetic were used to determine the inhibiting parameters. The endophytes that produced the most promising effects were identified using microscopy and MALDI-TOF techniques. Results22 extracts were obtained from Cola nitida and Cola acuminata endophytes extracts (16 and 6 respectively. Crude extracts and silver nanoparticle). The most active material were the crude extracts from Cola acuminata endophytes were found to be the most active preparations. The MALDI-TOF identification method yielded the designation of NPMRU 6508, NPMRU 6511, NPMRU 7045 and NPMRU 7063 as Bacillus cereus. Furthermore, NPMRU6113 and NPMRU7047 were identified as Brevibacterium sp. ConclusionThis study supports the use of endophytes derived from Cola acuminata and Cola nitida roots to combat four bacterial strains involved in the development of antibiotic resistance.