Antibacterial Activity of Bacteriophages and Extracts of Caesalpinia decapetala and Parrotiopsis jacquemontiana Against Pseudomonas aeruginosa and Staphylococcus aureus

Abstract

The emergence of antimicrobial resistance is one of the burning issues mankind faces.  The discovery of new antibiotics has declined significantly, and existing antibiotics are often ineffective against many MDR bacterial strains. Aqueous extracts of Caesalpinia decapetala and Parrotiopsis jacquemontiana were prepared in this study. Phytochemical analysis and antibacterial activity of extracts at a concentration of 6000µg/ml were examined against two multi-drug-resistant (MDR) bacterial species, Pseudomonas aeruginosa and Staphylococcus aureus. Spot assay was done to assess the lytic activity of bacteriophages against the MDR strains. The synergistic effect of extracts and bacteriophages was examined using a mixture of specific concentrations of extract and bacteriophages. Phytochemical screening revealed the presence of different phytochemicals in the root and stem extract of the plants including phenols, phlobatanins, coumarins, glycosides, and terpenoids. The well-diffusion assay revealed that the stem extract of C. decapetala demonstrated the highest activity against P. aeruginosa (PA2) with a 13mm zone of inhibition (ZOI), followed by P. jacquemontiana with an 11.5mm ZOI. In contrast, the lowest activity (9.7mm ZOI) was exhibited by the root extract of C. decapetala against  S. aureus. The synergistic study demonstrated that the stem extracts of both P. jacquemontiana and C. decapetala exhibit inhibitory activity against the bacteriophages. The combined application of plant extract and bacteriophage against selected MDR strains led to a 60-70% reduction in the zone of inhibition compared to their individual effects, suggesting a strong antagonistic interaction.