**3. Results and discussion**

*In vitro* antibacterial activity of different plant extracts from 10 selected plants was tested in relation to 11 bacterial strains. Intensity of antibacterial activity depended on the species of

microplate was prepared by dispensing 100 μL of Mueller-Hinton broth (Torlak, Belgrade) into each well. A 100 μL from the stock solution of tested extract (concentration of 40mg/ml) was added into the first row of the plate. Then, two-fold, serial dilutions were performed by transferring 100 μl of solution from one row to another, using a multichannel pipette. The obtained concentration range was from 20 mg/ml to 0.156 mg/ml. Ten microlitres of each 106 CFU/ml bacterial suspension was added to wells. Finally, 10 μL of resazurin solution was added. Resazurin is an oxidation-reduction indicator used for the evaluation of microbial growth. It is a blue non-fluorescent dye that becomes pink and fluorescent when reduced to resorufin by oxidoreductases within viable cells (Figure 1.). The inoculated plates were incubated at 37°C for 24h. MIC was defined as the lowest concentration of the tested plant

Antibiotic cephalexin, dissolved in Mueller-Hinton broth, was used as positive control. Solvent control test was performed to study an effect of 10% DMSO on the growth of bacteria. It was observed that 10% DMSO did not inhibit the growth of bacteria. Each test included growth control and sterility control. All tests were performed in duplicate and

All statistical analyses were performed using SPSS package. Mean differences were established by Student's *t*-test. In all cases *p* values <0.05 were considered statistically

Fig. 1. Plate after 24 h in resazurin assay (pink colour indicates growth and blue means

*In vitro* antibacterial activity of different plant extracts from 10 selected plants was tested in relation to 11 bacterial strains. Intensity of antibacterial activity depended on the species of

extracts that prevented resazurin color change from blue to pink.

MICs were constant.

inhibition of growth)

**3. Results and discussion** 

significant.

**2.1.5 Statistical analysis** 

bacteria, plant species and the type of extract. The MIC values were in range from 0.019 mg/ml to >20mg/ml. In relation to positive control (cephalexin MIC 0. 00156 - >1mg/ml), the extracts showed lower activity. In general, according to obtained results, the following remarks could be made:

