Synergistic Antibacterial Potentials of Ocimum gratissimum, Honey and Ciprofloxacin against some Multiple Antibiotic-Resistant Bacteria Isolated from Stool Samples

This study investigated the synergistic antibacterial potentials of Ocimum gratissimum (O. gratissimum) leaf acetone extract, honey, and ciprofloxacin against some multiple antibiotic-resistant bacteria. Multiple antibiotic-resistant bacterial isolates from stool samples of diarrhea patients and their typed cultures were subjected to inhibitory assay by mixtures of extract and honey, extract and ciprofloxacin, honey and ciprofloxacin, and extract, honey and ciprofloxacin using tube dilution method. Killing rate and mechanisms of action of the mixtures on the susceptible pathogens were determined. The multiple antibiotic resistance indices of the test organisms (MARI) ranged from 0.7 to 1.0. Extract, honey, and ciprofloxacin mixture at ratio 1:1:1 exerted the lowest minimum inhibitory concentration on E. coli, P. aeruginosa ATCC 10145, E. coli ATCC 25922, and S. typhi ATCC 14028 at 1.56×10-3 mg/mL compared with ciprofloxacin (3.13×10-3 mg/mL). Highest potassium, sodium, and protein leakage was induced by extract and honey mixture (97.4 cmol/g) in E. coli, extract, honey, and ciprofloxacin mixture (65.2 cmol/g) in B. cereus, and extract, honey, and ciprofloxacin mixture (21.6 mg/mL) in B. cereus, respectively. Extract, honey, and ciprofloxacin mixture exerted highest killing rate on B. cereus after 24 h (1.3×101 cfu/mL). These findings revealed a high synergistic antibacterial potential of O. gratissimum leaf acetone extract, honey, and ciprofloxacin against multiple drug-resistant bacteria, thus, implying their potential use in diarrhea treatment.