Antibacterial activity of seed extracts of Callistemon lanceolatus DC on uropathogenic bacteria

Abstract

Urinary tract infections are a major public health problem in developing countries. The spread of microbial drug resistance has become a global threat, challenging public health, and can result in increased illness and even lead to death in the chronic stages of infection. There is a desire to identify and exploit newer, ecologically friendly antimicrobial agents from natural sources to overcome this problem. This work was carried out to investigate the antibacterial potential of Callistemon lanceolatus DC seed extracts against 11 isolates of uropathogenic bacteria. Bacteria isolated from urine samples were collected from the Krishna Rajendra Hospital, Mysore, India and were subjected to biochemical tests followed by standard procedures for bacterial identification. The uropathogens were then tested for susceptibility to antibiotics using an assay following the Kirby–Bauer method. Phytochemical analyses of seed extracts of C. lanceolatus DC were carried out to identify the various phytocomponents. Antibacterial activity against 11 uropathogenic isolates using petroleum ether, chloroform, ethyl acetate, and methanol seed extracts of C. lanceolatus were carried out following the Kirby–Bauer disc diffusion method. The identities of the bacteria were confirmed by the biochemical tests. Antibiogram assays showed the sensitivity of the pathogens towards the test antibiotics. The phytochemical analyses showed the presence of carbohydrates, saponins, and phytosterols in all the test solvent extracts; alkaloids, tannins, and amino acids were absent from all the test solvent extracts. Tests to determine the antibacterial activity of seed extracts of C. lanceolatus against 11 isolates of bacteria showed significant activity against Staphylococcus aureus in petroleum ether and chloroform extracts; the ethyl acetate and methanol extracts showed significant activity against Proteus mirabilis . All the test solvent extracts showed the least activity against Acinetobacter baumannii . Petroleum ether, ethyl acetate, and methanol extracts also showed the least activity against Citrobacter freundii ; only ethyl acetate showed moderate activity against Enterococcus faecalis . The methanol extract showed moderate activity against Escherichia coli . Ethyl acetate and methanol extracts showed a moderate zone of inhibition against Klebsiella pneumoniae . This study shows that C. lanceolatus has an inhibitory effect on uropathogenic bacteria. The antibacterial activity of this plant could be exploited as a therapeutic agent for further investigation of the bioactive compounds responsible for antibacterial activity.