الفهرس 
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Abstract
Summary
The study aims to evaluate the antibacterial effect of some medicinal plants, in addition to the synergistic effect of them with some antibiotics against some pathogenic bacteria. Eleven medicinal plants (coriander, parsley, ginger, olives, chamomile, licorice, henna, myrtle, oleander, sweet basil, and Roselle) were used, where the alcoholic and aqueous extract was prepared for each medicinal plant. Antibacterial activity was evaluated for plant extracts, using the well diffusion method, and antibacterial activity for some types of antibiotics was evaluated using the disc diffusion method. The value of the minimum inhibitory concentration of plant extracts alone was estimated using the micro-dilution method in the liquid media and the well diffusion method in the solid media. The synergistic effect between some types of plant extracts and resistant antibiotics was evaluated using the well diffusion method. Moreover the mixture of plant extracts, chitosan and silver nanoparticles were tested as antibacterial agent.
The obtained results can be summarized as follows:--
1- Evaluation of antibacterial activity of plant extracts:
a- Against some types of Staphylococcus aureus, the results showed that the ethanol extract from medicinal plants has better effect against most of the tested bacteria than the aqueous extract.
The highest antibacterial activity was obtained by aqueous roselle extract, followed by ethanolic roselle extract, aqueous sweat basil extract and ethanolic parsley extract (18.5, 17.5, 14.5and 14 mm, respectively).
Aqueous and alcoholic extracts of coriander, oleander, ginger, aqueous parsley extract, and ethanolic sweat basil extract do not affect on tested bacteria.
b- Against some lactose -fermenting bacteria, all plant extracts inhibit the bacterial growth, but to varying degrees.
The results showed that the highest inhibition was observed by ethanolic myrtle extract, followed by aqueous myrtle extract and aqueous chamomile extract (20, 19, and 18.5 mm respectively).
The aqueous and ethanolic extracts of roselle is considered one of the most inhibiting of the growth of some types of lactose-fermenting bacteria, while the aqueous extract of sweat basil affects only on E.coli 2, and also, E.cloi E was only affected by aqueous henna extract and ethanolic parsley extract.
c- Against some non-lactose fermenting bacteria, the results showed that the highest inhibition was noticed by the ethanolic ginger extract, followed by ethanolic roselle extract and aqueous roselle extract (22, 18.5, and16 mm, respectively).
The aqueous and ethanolic extract of roselle is considered one of the most inhibiting of the growth of some types of non-lactose fermenting bacteria, while the aqueous sweat basil extract and ethanolic ginger extract affected only salmonella typhi. Listeria ATCC 1916 was inhibited by ethanolic sweat basil extract only.
2- Eight antibiotics were selected to study their antimicrobial activity against 32 pathogenic bacterial strains 99% of bacterial strains were resistant to Pencillin while 81, 78 and75% of bacterial strains were resistant to Cefadroxil, Erythromycin and Ampicillin, respectively. Moreover, 37% of bacterial strains were resistant to all tested antibiotics followed by 12% and 9% of the strains were resistant to six and 7 tested antibiotics, respectively.
3- Minimum inhibitory concentration of plant extracts was detected by agar diffusion and micro diffusion methods in solid and liquid media, respectively. 20l was the value of MIC for all tested extract in solid media and ranged from 120-200l in liquid media. Data also clearly showed that the licorice and myrtle extracts which recorded the lowest values of MIC in solid medium gave the highest value in liquid medium (200) whereas the vice versa was true for roselle extracts.
4- Bacteriocidal activity was obtained by aqueous and ethanolic roselle or ethanolic licorice extracts against Enterobacter cloacae MB 11506_1CHB4I and by aqueous and ethanolic roselle or myrtle extracts against Citrobacter Freundii 22054_1 CHB2. Whereas bacteriocidal effect of Klbsiella pneumonia ATCC 00607 was obtained by aqueous and ethanolic roselle, aqueous licorice and aqueous myrtle.
5- The combination of roselle extracts to myrtle extracts reduced their antibacterial activity against citrobacter freundii 22054_1 CHB2 about 81 to 86% comparing to the effect of roselle extract (20µl) alone and about 60 to 71% comparing to the effect of myrtle extract (20µl) alone.
6- Four chitosan or silver nanoparticles concentrations ranging from 0.125 to 1.0 mg/ml were tested against the pathogenic bacterial tested strain. The results indicated that the silver nanoparticles inhibit the bacterial growth of the tested bacteria, unlike chitosan, does not cause any effect. Increasing concentration of silver nanoparticles lead to increasing the value of inhibition zone to reach the highest value at 1.0mg/ml against all tested strains. At1.0mg/ml silver nanoparticles,the antibacterial activity increased 1.12,1.20 and 1.25 fold of inhibition against Enterobacter cloacae MB11506_1CHB4, Citrobacter freundii 22054_1 CHB2 and Klbsiella pneumonia ATCC00607, respectively comparing by using ethanolic roselle extract at 20 µl using agar diffusion method .
7- The supplementation of plant extract with antibiotics in sub recommended dose may increase the efficient of plant extract as antibacterial agent as seen for roselle extracts (aqueous & ethanolic) and aqueous myrtle extract with pencillin G which recognized as synergistic effect against Citrobacter freundii 22054_1 CHB2. On the other hand, mixing of ethanolic roselle extract with erythromycin decreased the efficient of plant extract as known as antagonistic effect against Klbsiella pneumonia ATCC 00607. Moreover, addition of cefadroxile to roselle (aqueous & ethanolic) and ethanolic licorice inhibit the effect of these agents on the growth of Enterobacter cloacae MB 11506_1CHB4 strain.
8- The results of Gas chromatography-mass spectrometry GC/MS analysis of ethanolic extract of Hibiscus sabdariffa, indicated to the presence of some major compounds in ethanolic extract of Hibiscus sabdariffa is scientific evidence in support the use of this plant as a medicinal preparation. The association of these volatile compounds in this variety of H. sabdariffa could justify the antioxidant, anticancer and antimicrobial activity of H. sabdariffa.