ملخصات لبعض ابخاثي

1. Detection of stx gene of E. coliO157:H7 in fresh sausage by
using polymerase chain reaction (PCR)
Iman Mohamed Ben Hamza*
Yousef Mohamed Elshrek**
ABSTRACT
PCR was used to detect and verify the existence of pathogenic Stx-encoding genes
Stx1 and Stx2 in E. coli O157:H7. Specific primers for these genes were designed
in order to detected and identify them. PCR products were later run through
agarose Gel Electrophoresis to verify the presence of those pathogenic genes.
Comparing the length of the amplified fragments genes 513 bp Stx1 and 482 bp
Stx2 with that negative control, positive control, marker, it was found out that the
positive control was Stx1 and Stx2 genes of E. coli O157:H7. The percentages of
Stx genes in bacteria E. coli 0157:H7 that were detected was 60.42%, the statistical
analysis for Stx results show that there were no significant differences at level (P<
0.05 ) between regions of study were detected of Stx1& Stx2 in all regions of
study which means most samples of regions study were contaminated with stx-
positive.
__________________________________________________________________
* Iman Ben Hamza researcher in Microbiological Department of Environment General Autherity -
Tripoli Libya
** Yousef Elshrek L professor in Food Science Department Faculty of Agriculture University of Tripoli
Libya.

2. Microbiological quality of fresh sausage
Marketed in Tripoli city, Libya
Yousef Elshrek * and ** Iman Hamza
Abstract
We investigated the microbiological quality of fresh beef sausages in different Tripoli regions
areas. Thus 100 samples were analyzed microbiologically. The results showed that all samples
were highly contaminated with bacteria; the mean of total plate count for (Al margaz )
sausage samples values for all regions of study was 2.5 x 108
CFU/gram, and the
range from (7 x 104
to 5.5x 109
CFU/g), there were no significant differences at
level (P< 0.05) between the regions of study. The general means of most probable
number of Coliforms for all regions of study was 1.4x103
Cell/gm, and the range
from (1.6 x 102
to 2.4 x 103
Cell/gm), there were significantly differences at level
(P< 0.01). The percentage of Escherichia coli that contaminated and isolated from
the sausage samples in Tripoli city butchers, were 81%, there were no significant
differences at level (P< 0.01 ) between regions of study. The percentage of E .coli
0157:H7 that contaminated and isolated, from the sausage samples in Tripoli city
butchers, were 48% there were no significant differences at level (P< 0.05 )
between all regions of study.
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* Yousef Elshrek L professor in Food Science Department Faculty of Agriculture University of Tripoli
Libya.
** Iman Ben Hamza researcher in Microbiological Department of Environment General Autherity -
Tripoli Libya

3. Microbiological quality of meat and meat products
Marketed in Tripoli city, Libya: Review
*1
Nura N Altajori and Yousef M. Elshrek2
ABSTRACT
The aim of this paper is to review some microbiological aspects of meat and meat
products distributed in different local markets in Tripoli city, Libya. Studies were
conducted separately and in different occasions, in the years 2005 – 2009.
Samples were collected from different places mainly, restaurants, hotels, houses
and other local markets in Tripoli area and its suburbs. Results indicated that beef
burger samples were highly contaminated with several pathogenic bacteria such as
E. coli (74.5%), E. coli O157:H7 (27.1%), S. aureus (28.8%) and Aeromonas
(18.6%). Meanwhile, fresh sausage samples were contaminated with
E.coliO157:H7 (39.3%) and salmonella (2.1 %). In addition, studies on chicken
burgers, found that % of E. coli and E. coli O157:H7 reached (10.9 %), and
(4.68%) respectively. Also studies on camel meat revealed presence of Aeromonas
(71%), A. hydrophilaand A. sobria (65% and 35%) respectively. In addition,
approximately 79% of camel meat samples were contaminated with S. aureus and
4% with Salmonella anatum, and 41% with E. coli, but no detection of E. coli
O157:H7 and Campylobacter in all samples. In another study regarding Libyan
Kofta (meat balls) it was found that percent of S. aureus reached (40%) in samples
collected from houses and 42% in those collected from hotels. in the case of fried
meat samples contamination with S. aureus was 7% in samples collected from
houses,43% from hotels, 23% from wedding halls, and 20% from restaurants.
Results also showed that 6.9%, 14%, 19.4% and 30% of the fried samples were
contaminated with E. coli O157: H7for samples collected from houses, hotels,
wedding halls and restaurants, respectively. In another study performed on 48

4. sausage samples using PCR technique biochemically confirmed the presence of E.
coli 0157:H7 virulence genes Shiga toxin genes (stx). Unfortunately, one could
conclude that meat and meat products marketed in Tripoli are of low quality from
microbiological view point and unsafe due to the high percentage of several
pathogenic bacteria. This reflects the low measures of quality control and no
concern regarding personal hygiene and sanitation and manufacturing practices.
Keywords: Meat, meat products and microbiological aspects
Clinical biochemistry Med. University of Benghazi Libya1
.
Food Science Department, Faculty of Agricultural University of Tripoli, Libya 2

5. EFFECT OF CALCIUM, ADENOSINE TRIPHOSPHATE,
AND NITRITE ON THE DEGRADATION OF
MYOFIBRILLAR PROTEIN (ATP)
Yousef Mohamed Elshrek
PhD Dissertation University of Missouri - Columbia 179 (1982)
Beef and chicken myofibrils were used as substrates to study the effect of CaCl2,
ATP, and beef muscle lysosomal enzymes on protein degradation. Degradation of
beef and chicken myofibrillar proteins was measured using sodium dodecyl
sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), water holding capacity
(WHC), and nonprotein nitrogen (NPN). The reactions were carried out at pH 5.5
and 7.0 at 4(DEGREES)C and 37(DEGREES)C for 1.5, 6, 24, 48, and 96 h. The
addition of CaCl2, ATP, or a mixture of CaCl2 and ATP to prerigor myofibrils
stimulated degradation of connection, myosin, M(,(alpha)) and M(,(beta)) proteins.
CaCl2 or ATP or a mixture of the two enhanced lysosomal protease activity at pH
5.5 and 7.0 and stimulated degradation of M(,(alpha)) and M(,(beta)) proteins. pH
optima of beef lysosomal enzymes were found at pH 7.0 and 5.0. Activity at pH
5.0 was 50% of that at pH 7.0. One mM CaCl2 , 5 mM ATP, 5 mM ADP, or 5 mM
AMP enhanced the proteolysis of the chicken myofibrillar proteins, actomyosin,
and connectin, while sodium nitrite decreased degradation of chicken myofibrillar
proteins at pH 7.0, 37(DEGREES)C. Sodium nitrite (NaNO2) had little influence
on enzyme activity in the presence of CaCl2 and/or ATP. Dilute salt-soluble
chicken breast myofibrillar proteins treated with NaNO2 were completely
degraded by lysosomal enzymes containing ATP and by a reaction mixture
containing lysosomal enzymes, ATP and CaCl2 Troponin T, troponin C, and
myosin light chains in the same sample were degraded by all treatments containing
lysosomal enzymes, CaCl2 and ATP. The influence of CaCl(,2), ATP, and
lysosomal enzymes independently and in combination on the water-holding
capacity (WHC) of beef myofibrillar proteins was also studied. WHC of beef
myofibrils reacted with lysosomal enzymes was enhanced by adding ATP, CaCl2 ,
or a mixture of the two, but was reduced in the presence of CaCl2 alone.
Keywords: Biological science, Food science
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