Antibacterial Activity of Pomegranate (Punica granatum) Fruit Peel Extracts Against Antibiotic Resistant Gram- Negative Pathogenic Bacteria

Fighting bacterial antibiotic resistance is a great challenge, and the researchers are in search of alternative therapies, the effective antibacterial biotherapeutics, in particular. This research aims to explore the antibacterial potentiality of pomegranate (Punica granatum) fruit peel extracts against gram-negative pathogenic bacteria having high MAR (multiple antibiotic resistance) indices. A total of 17 gram-negative pathogenic bacteria: Escherichia coli (n=5), Proteus spp. (n=4), Klebsiella pneutnoniae (n=2), Pseudomonas aeruginosa (n=3), Acinetobacter baumannii (n=3), were subjected to susceptibility testing by disc diffusion method using 15 antibiotics, and the MAR indices were calculated. The antibacterial activities of APE (pomegranate fruit peel aqueous extract) and PEE (pomegranate fruit peel ethanolic extract), for the test bacteria, were determined by disc diffusion, while agar dilution technique was followed to determine the MIC (minimum inhibitory concentration) values of the extracts. The bacteria tested, displaying varied MAR resistance phenotypes, had resistance to 7-14 antibiotics, and the MAR indices for the bacterial isolates ranged 0.46 -0.93. The PEE and APE both showed antibacterial activities, with respective ZDI (zone diameter of the inhibition) values of 14.7 +/- 5.32 mm and 17.53 +/- 5.72 mm (at 1 mg/disc), and 13.3 +/- 5.69 mm and 16.65 +/- 7.55 mm (at 2 mg/disc). The PEE and APE MICs ranged 2.5-3.3 mg/mi and 5-20 mg/ml, respectively, for the test bacteria. Thus, fruit peel of pomegranate might be useful in the preparation of antibacterial therapeutic agents, alternative to antibiotics, in order to combat the life-threatening infections of multiple antibiotic resistant gram-negative bacteria.