The Antibacterial Effect of Aqueous Extract of Garlic against Resistant Enterococci

Abstract       Background and Objective: Enterococci are relatively nonvirulent bacteria that rarely cause disease. Antimicrobial treatment of Enterococci is often challenging due to their antibiotic resistance. This study aimed to investigate the antibacterial activity of aqueous extract of garlic against Enterococcal isolates.     Methods: In this descriptive study, 120 Enterococcus isolates including 70 multidrug-resistant isolates were collected from hospitals of Babol, Iran. Isolates’ susceptibility to different antibiotics and the antibacterial activity of garlic extract were assessed using methods of minimum inhibitory concentration (MIC) measurement. The experiments were performed according to the Clinical & Laboratory Standards Institute guidelines, using Tryptic soy broth medium and disc diffusion method.       Results: Among the 120 Enterococcal isolates, 95 (79.2%) and 25 isolates (20.8%) were E. faecalis and E. faecium, respectively. Of the all Enterococcal isolates, the highest resistance was to erythromycin (95.8%), tetracycline (88.3%) and ampicillin (65.8%). While, the minimal level of resistance was to chloramphenicol (6.8%), vancomycin (20%) and ciprofloxacin (25%). Also, 53.3% of Enterococcal isolates showed simultaneous resistance to at least three antibiotics (tetracycline, erythromycin and ampicillin). Such resistance in E. faecium isolates was higher compared to E.faecalis (68% vs. 55.7%). The range of antibacterial activity of garlic extract against isolated Enterococci was determined by growth inhibition zone of 16.8 ± 1.8 mm and MIC of between 4 to 32 mg/ml.       Conclusion: This study indicates the clear anti-enterococcal effect of aqueous extract of garlic and confirms the use of garlic in treatments by medicinal plants.