Pasteur Institute of Iran

  Biofilm of Pseudomonas aeruginosa, an opportunistic pathogen, can cause serious health problems, such as chronic infections, especially in immunocompromised patients. Many studies have suggested administration of new generation of antibiotics, as P. aeruginosa biofilms have developed high resistance to antimicrobial drugs. This study reports the inhibitory effect of three medicinal plant extracts and an essential oil on biofilm formation by a clinical isolate of P. aeruginosa. In this study biofilm formation of P. aeruginosa strain 214 was determined in presence of three plant extracts, Cyclamen coum, Dianthus orieltalis and Origanum majorana, and Zataria multiflora Bio essential oil. Minimum Biofilm Inhibitory Concentrations (MBICs) were determined by microdilution techniques and XTT assay. The C. coam extract and Z. multiflora Bio essential oil inhibited biofilm formation completely at concentrations<0.062 mg/ml and 4 µl/ml, respectively. The D. orientalis and O. majorana extracts did not inhibit biofilm formation at the used concentrations (0.003 – 8 mg/ml). The results of this study indicate that some plant extracts at low concentrations may provide a complementary medication for biofilm-associated infections. Further evaluations are required to validate the antibiofilm effect of these medicinal plants.

Introduction: Increasing of food-related diseases has led to the perception of diet importance. Plant-derived products (especially tea) as important sources of antioxidant and antimicrobial compounds play a major role in reducing food pathogens. In this study, total phenolic content, antioxidant and antimicrobial activity of four tea extracts including green tea, white, black and red teas were evaluated. Methods: The total phenolic amount was determined using Folin–Ciocalteu method and 1-diphenyl-2-picryl hydrazyl radical (DPPH) method was used for antioxidant activity measurement. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of tea extracts against eight species of tested bacteria (Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumonia, Saprophyticus Staphylococcus, Enterococcus faecali, Acinetobacter baumannii, Proteus mirabilis and Serratia marcescens) were evaluated by microdilution technique. Results: The results of this study showed that green tea and white tea extracts had the highest total phenolic content and antioxidant scavenging activity. Also, a strong positive correlation was observed between phenolic content and antioxidant activity in green tea and red tea. Conclusion: All four tea extracts showed inhibitions of several microorganisms. However, gram-negative bacteria were more resistant to inhibitory effects of tea extracts. As a result, non-fermented tea extracts showed more antioxidant activity and inhibition effect against tested bacteria.