الفهرس 
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Abstract
In this study, 512 milk samples were collected from different sources.The
incidence of Listeria among the different ruminant species revealed that the percentage of Listeria isolation reached 6.1%. The isolated Listeria spp. were
distributed as 9 strains from cows, 8 strains from buffaloes, 6 strains from goats, 8
strains from ewes and 4 strains from she –camels raw milk. The Listeria spp were
distributed as 7 strains of L. monocytogenes, 4 strains L. innocua, 8 strains L.
welshimeri, 7 strains L. seelegeri and 5 strains L. grayi in a percentage of 1.4%,
0.8%, 1.6%, 1.4% and 0.98%, respectively. The results of virulence study revealed
that all of the tested Listeria isolates were strong positive for Congo red after 24 hrs.
The Listeria monocytogenes isolates induced severe vaculation and detachment in
vero cells but the other Listeria spp. did not induce any change. Virulence of the
Listeria isolates was also investigated by i/p injection to mice, intraocular distillation
in rabbits and intraallantoic inoculation in ECG. Death occurred to mice and chick
embryos and eye inflammation in rabbits within 24h after injection in an incidence of
100% (toxigenic). On the other hand the suspected isolates of L. innocua, L. seelegeri,
L. welshimeri and L. grayi showed negative results (non toxigenic). The results of
biofilm formation showed that the L. monocytogenes from goat and she-camel show
high degree to form biofilm to plastic surface than other strains although L.
monocytogenes type 4 has a strong degree to form biofilm with glass surfaces than
type 1 while L. innocua, L. grayi and L. welshemeri showed a lesser degree to form
biofilm to plastics surface. L. seelegeri from cow milk and goat milk showed high
degree to form biofilm to plastic surfaces. L. innocua from cow’s milk and buffalo’s
milk has strong degree to form biofilm with glass surface while other Listeria spp (L.
welshemeri and L. grayi) ranged from moderate to weak. The antibiogram for Listeria
isolates revealed that all isolates showed resistance for the following antibiotics:
cloxacillin, oxacillin, pefloxacin, flumoquine, cephalosporin, bacitracin, lincomycin,
clindamycin. It was obvious that the Listeria isolates showed a significant effect of
Listeria on the level of nitric oxide and the effect on the lysozyme level was also
significant except in buffalo milk. Virulotyping analysis of the isolates was screened
for the presence of four virulence genes (hly, plc, act and iap) by conventional PCR
which showed that all genes were present in the L. monocytogenes while absent in
other species except L. seelegeri which carried the hly gene. The outer membrane
proteins analysis by the SDS-PAGE was used to establish the relationship between the
related isolates. The protein bands of all of the examined isolates of 100-110 kDa
protein bands were detected in all isolates from different sources referring to Listeria
adhesion proteins) (LAP). Protein bands of 53-73 kDa appeared as major bands in all
the isolates of L. monocytogenes refers to the invasion associated proteins (p60) and
also for internalins B (inlB) Protein bands between 27-32 kDa appeared all the
isolates of L. monocytogenes referring to metlloprotease (MPI) protiens. The
Extracellular protein profiles of the L. monocytogenes isolates from different milk
source were determined by SDS-PAGE show that the 50-70 kDa protein bands were
detected in all isolates from different sources refers to listeriolysin O (LLO). Protein
bands of 55-63 kDa appeared as major bands in all the isolates of L. monocytogenes
referring to cell wall hydrolase (peptidoglycans). Protein bands between 29-33 kDa
appeared in all of the isolates of L. monocytogenes which refers to phospholipase C. The sequencing of the hly gene revealed that the L. monocytogenes from cow milk
and she-camels milk showed maximum similarity % (86% and 85% respectively)with L. monocytogenes strain FSL F2-695 serotype 4a while L. monocytogenes from goat milk and ewe milk showed maximum identity % (88% and 91% respectively) with L. monocytogenes strainATCC 19117 serotype 4d.