الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Drug resistance in bacteria is increasing and the pace at which new antibiotics are being produced is slowing. There has been an increasing interest in herbal extracts and their essential oils during recent years because of the need of new therapies against microbes to develop alternative natural, safe, inexpensive and effective.
The present study aimed to determine the antibacterial activity of some medicinal herb extracts against bacterial isolates and reference strains representing both Gram positive and Gram negative bacteria.
This comparative experimental study was carried out during the period from October 2011 to February 2012. A total of five herbs collected from EL-Shefaa Center for Herbal Medicine, namely: mint, green tea, ginger, garlic and aloe vera were tested for their antibacterial activity against two bacterial reference strains (MRSA and P. aeruginosa) and two bacterial isolates (E. faecalis and E. faecium).
The procedure of this study included:
1- Purification and confirmation of the tested organisms.
2- Preparation of herbal extrats:
a- Green tea and mint extracts: Thirty grams of each herb were boiled in 100 ml DW for 15 min.
b- Garlic extract: Thirty grams of the peeled garlic were homogenized in 100 ml DW in a mixer.
c- Ginger extract: Thirty grams of ginger powder were soaked in 100 ml of 95% ethanol for 24 hours, then air dried to let evaporation of ethanol.
d- Aloe vera extract: The gel was heated for stabilization and then pulverized in an electric blender.
All herbal extracts were sterilized by filtration through a sterile syringe membrane filter with 0.45 µm pore size.
3- Antimicrobial assays:
a- Broth dilution method for determination of MIC of the herbal extracts, using five serial concentrations.
b- Agar well diffusion method: The selected herbs were screened against the examined bacterial species (MRSA, P.aeruginosa, E.faecalis, E.faecium) at five different concentrations.
c- Synergy studies: The checker board method was used to obtain the fractional inhibitory concentration (FIC) index of extract combinations. The results were interpreted as synergy (FIC≤0.5), addition (0.5<FIC≤1), indifference (1<FIC≤4) or antagonism (FIC>4).
The 10 different combinations used against the tested isolates were as follows:
1-Garlic + green tea 6-Green tea + mint
2-Garlic + aloe vera 7-Green tea + ginger
3-Garlic + mint 8-Aloe vera + mint
4-Garlic + ginger 9-Aloe vera+ ginger
5-Green tea + aloe vera 10-Ginger + mint
In addition antibiotic disc diffusion method (Kirby-Bauer) was used to study the susceptibility of the tested bacteria and to compare the inhibition zone of antibiotic and herbal extracts.
The results of this study showed that:
1- All the aqueous herbal extracts and ethanolic ginger extract exhibited antibacterial activities against all the tested organisms with varying degree.
2- Garlic extract showed the maximum activity with MIC values ranging from 18.8 to 9.4mg/ml; and IZD of 45mm for MRSA, 30mm for P.aeruginosa and 18mm for E.faecium.
3- AV extract showed the minimum activity with MIC value of 300mg/ml. No inhibition was revealed for all the tested bacteria using the agar well diffusion method.
4- Mint, green tea and ginger extracts followed garlic, with MIC values ranging from 37.5 to 150mg/ml against all the tested organisms.
5- All the examined extracts were more effective in inhibiting Gram positive bacteria when compared with Gram negative bacteria.
6- Comparing the results of IZD of antibiotics and herbal extracts, herbal extracts were more effective than antibiotics against MRSA, E.faecalis, E.faecium, while antibiotics were more effective than herbal extracts against P.aeruginosa.
It can be concluded from this study that:
- Herbal extracts can provide adequate degree of protection against the tested organisms.
- Among the tested organisms MRSA was the most susceptible while P.aeruginosa was the least susceptible organism.
- Among the tested herbs, garlic was most effective and aloe vera was least effective.
- The majority of combinations displayed an indifference effects. Additive effects were found for garlic with aloe vera, aloe vera with ginger and aloe vera with green tea.
RECOMMENDATIONS
1- Garlic can be utilized for the development of broad spectrum antibacterial agents as it has wide spectrum antibacterial activity.
2- The use of herbal extracts in combination is recommended to reduce the concentration used and to widen the spectrum activity.
3- Further studies are recommended for measuring antibacterial activities of different types of herbs on a large scale.
4- Further studies are required to examine the synergistic effect of antibiotics with herbal extracts.