الفهرس 
INTRODUCTION
Food borne bacteriaOnly 14 pages are availabe for public view
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Abstract
There is a growing consumer demand for food that is free of chemical food additives, especially of chemical antimicrobials. It is therefore necessary to develop alternative natural, safe, inexpensive and effective methods for controlling bacterial infections in and through food. They may replace conventional chemical antimicrobials.
In this study, the work aimed at investigating the antibacterial activity of some medicinal herb and spice extracts on some food borne bacteria. It included the determination of the concentration of individual extracts of the selected herbs and spices required for inhibition of the tested bacteria. The antimicrobial extracts found active against major food-borne pathogens were subjected to further studies of synergism.
A total of 5 herbs and spices collected from markets in different districts in Alexandria namely: Garlic, thyme, cinnamon, marjoram and clove were tested on the food borne bacterial isolates representing Gram positive and Gram negative bacteria obtained from food samples referred to the Central Lab of HIPH for investigation. All the selected food borne bacterial isolates were purified and confirmed using standard methods.
Plant extracts were prepared by boiling thirty grams of each tested herb except garlic in DW for 10 min, the extract was filtered, centrifuged and sterilized by filtration through a sterile syringe membrane filter with 0.20 - 0.45 µm pore.
Antimicrobial assays was done on each type of isolated food borne bacteria using the herb and spice extracts by:
1-Broth dilution method: The MIC of the active herbal extracts were tested using two fold serial broth dilution method at concentrations (300, 150, 75, 37.5, 18.75) mg/ml
2- Disc diffusion method: The selected herbs were screened against the four selected food borne bacteria (E.coli, S.aureus, Salmonella, Shigella) at five different concentrations.
3- Synergy studies:
The tests were performed to study the antibacterial synergistic effect of herbal extracts combinations using the checker board method 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 results of this study showed that:
1- All the aqueous plant extracts exhibited antibacterial activities against all the tested organisms with varying degree.
2- Garlic extract showed the maximum activity with MIC values ranging from 18.75 to 37.5 mg/ml also it caused inhibition of all tested bacterial isolates using the disc diffusion method.
3- Cinnamon and thyme extracts followed garlic with MIC values ranging from 75 to 150 mg/ml against all the tested strains