Antibacterial activities of potential antibiotic-producing bacteria and indigenous plants against antibiotic-resistant bacteria

Abstract

Antibiotic resistance is a significant global public health problem, intensified by anthropogenic activities. The resistance contributes to longer hospital stays, increased health care, and high death rates. Natural compounds from medicinal plants and bacteria are attractive alternatives for the development of novel antibiotics and ultimately combating antibiotic resistance. The study aimed to isolate, and screen crude plant extracts and bacteria for antibacterial properties. Selected test bacteria; Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Proteus mirabilis MN029 were used in the screening of antibacterial properties of selected plants and potential antibiotic-producing bacteria. Long-read PacBioⓇ HiFi technology was used to sequence Proteus mirabilis-MN029 and the strain was used as a model for multi-drug resistant bacteria in evaluating the antibacterial properties of plant crude extracts. The Proteus mirabilis-MN029 genome comprised of a single chromosome, 38.5% G+C content and 3,988,563 bps in length, acquired and chromosomally encoded antimicrobial resistance genotypes to clinically relevant antibiotics, virulence factors, drug targets and transporters. Potential antibiotic-producing bacteria were also isolated from soil and water samples, the isolates that inhibited at least four test bacteria were subjected to Gram staining, biochemical testing, and antibiotic susceptibility testing. Four promising antibiotic-producing bacteria were sequenced using short-read sequencing technology on the Illumina platform. The potential antibiotic-producing bacteria were identified as Paenibacillus elgii-KM_B45, Brevibacillus laterosporus-KM_C76, Paenibacillus oleatilyticus-KM_D13 and Paenibacillus oleatilyticus-KM_D46, their genomes revealed 23 biosynthetic gene clusters associated with antibacterial properties. Pterocarpus angolensis, Aloe zebrina and Aloe littoralis were also tested 1 for antibacterial effectiveness against the test bacteria. Maceration was used to extract plant crude extracts using solvents of different polarities. The primary screening was conducted using Kirby Bauer Disc diffusion, while microdilution assay was employed as a secondary screening for determining the minimum inhibitory concentration of the medicinal plants against the test bacteria. Among the three tested medicinal plants, P. angolensis inhibited most of the test bacteria compared to A. littoralis and A. zebirna. The highest activity was demonstrated at MIC of 0.075 mg/ml by A. littoralis and A. zebrina ethylacetate root extracts against S. aureus. The results of antibacterial activities associated with the selected bacteria and plants provide a great opportunity for further research, which will focus on the purification of the secondary metabolites for use in the development of new antibiotics.