BACKGROUND AND OBJECTIVE In traditional medicine, pomegranate is used for the treatment of intestinal worms and diarrhea. This study aimed to examine the antibacterial activities of pomegranate extracts on biofilm structures and planktonic forms of six pathogenic bacteria.

METHODS: In this study, the inhibitory effect of the extracts on planktonic forms was determined, using disc diffusion method. Minimum inhibitory concentration (MIC) of 0.02 mg/ml and maximum inhibitory concentration of 50 mg/ml were determined, using broth macrodilution. Anti-biofilm effects at 5 mg/ml, 10 mg/ml, and 20 mg/ml concentrations were assessed using microtiter plate method. Also, biofilm formation, biofilm degradation, and dehydrogenase enzyme activity were determined by crystal violet staining.

FINDINGS: Discs impregnated with pomegranate extracts inhibited the growth of test bacteria by 50% (P<0.01). However, no inhibitory effect was detected on streptococcus pneumoniae, pseudononas aeruginosa, or klebsiella pneumonia (p>0.05). In the broth medium of MIC test, the extracts could inhibit the growth of all bacteria (70%). These extracts damaged the biofilm structures by 50% (minimum) and 95% (maximum), respectively. The inhibitory effect of the extracts was dependent on the extract concentration and type of solvent. Pomegranate extracts were most efficient in inhibiting the biofilm formation of staphylococcus aureus (95.84%). The greatest eradication of biofilm structures was observed in the biofilm of pseudomonas aeruginosa (51.48%). Also, the highest decrease in metabolic activity was observed in bacillus cereus (77.13%).

CONCLUSION: In this study, the inhibitory effect of pomegranate extracts on planktonic forms and biofilm structures was confirmed. As it was shown, the inhibitory effect was correlated with the solvent type and extract concentration.