الفهرس 
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Abstract
With increasing the resistant of bacteria and fungi against common antibiotics, there was a corresponding rise in the universal demand for
natural antimicrobial therapeutics. Herbal medicines have widely been used
and now form an integral part of the primary health care in many countries.
The aim of the present study was to assess the antimicrobial and
synergistic effect of some medicinal plant extracts alone and with certain
commercial antibiotics against some microbial stains.
The plant materials used in this study were Achillea santolina,
Artemisia herba alba, Capparis oriantalis, Peganum harmala,
Pituranthos tortuosus and Thymus capitatus which are growing in
Marsa Matrouh, Egypt. Powdered plant materials of all selected plants
were extracted with aqueous, chloroform and methanol and tested
for antibacterial and antifungal activity using agar disc diffusion
method. Results revealed that, methanol extracts of Achillea santolina,
Artemisia herba alba, Capparis oriantalis and Peganum harmala and
chloroform extracts of Pituranthos tortuosus and Thymus capitatus had
the most noticeable antibacterial activity. On the other hand, these
extracts showed weak antifungal effect.
The previous mentioned plant extracts were prepared at different
concentrations (200 –1.56 mg/ml) to determine their MICs50 using
broth microdilution method. Each tested plant extract recorded variable
MICs50 values according to each tested bacteria.
The susceptibility of the tested bacteria to twenty-four different
commercial antibiotics representing 16 different classes was evaluated by using agar disc diffusion method. It was found that the antibiotic
resistance in this experiment varied in its incidence depending on
antibiotic type and bacterial species. Also, data obtained revealed
that all investigated bacteria were completely resistant to only two
antibiotics cefepime and aztreonam.
According to the previous experiments, six different plant extracts
(including four methanol extracts of Achillea santolina, Artemisia
herba alba, Capparis orientalis and Peganum harmala and two
chloroform extracts of Pituranthos tortuosus and Thymus capitatus)
that had the best antibacterial activity were used in combinations
with the ineffective antibiotics using disk diffusion method in order to
evaluate the antimicrobial activity of plant extracts and antibiotics
interactions. There were many synergistic interactions between the
investigated plant extracts and antibiotics against the tested bacteria.
It was revealed that, the combination between Thymus capitatus extract
and cefepime gives the highest synergistic effect.
The examination of cell morphology through transmission electron
microscopy (TEM) images of treated bacterial cultures was carried out
to assist understanding of the antimicrobial action chloroform extract
of Thymus capitatus and cefepime antibiotic against S. dysenteriae
pathogenic bacteria. The resultant TEM images demonstrated that
untreated S. dysenteriae cells had evenly distributed cytoplasm without
alterations of the internal structures; whereas the treated cells showed
various forms of morphological alterations as a rupture in the bacterial
cell, shrinking of cellular content with irregularity and distortion in
the cell wall with released cellular components.
Finally, we elucidate the effect of cefepime antibiotic, chloroform
extract of Thymus capitatus and their combination mixture on the rate of S. dysenteriae infection in comparison to controls (non-infected and
infected) in mice. The number of bacterial colonies in blood, livers and
spleens of mice were measured in order to determine the ability of the
plant extract alone or its combination with the antibiotic to reduce the
infection load of tested bacteria. Also, some biochemical parameters
were measured such as liver enzymes (ALT and AST), renal function
(urea and creatinine) to evaluate these treatments on livers and kidneys
of mice. Our findings revealed that, the extract of Thymus capitatus
showed a protective role against S. dysenteriae infection in mice. Also
it had a potential synergistic role with cefepime antibiotic.