الفهرس 
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Abstract
Pasteurella multocida is the common cause of respiratory disease in small (sheep and goat) and large (cattle and buffalo) ruminants causing high economic losses. A total of 36 P. multocida isolates were detected from 451 samples (8%). Lung tissues showed the highest percentage of Pasteurella multocida isolation (23/189) as a percentage (12%), followed by nasal swabs (13/262) as a percentage (4.9%). These isolates were confirmed microscopically, biochemically and rabidly by using Vitek2 compact system. PMT-ELISA and mouse lethality test was used for differentiation between toxigenic and non-toxigenic isolates. Polymerase Chain Reaction (PCR) system was used for detection of tox A gene and multiplex PCR was used for capsular serotyping of toxigenic isolates .A total of 11 isolates showing to be toxigenic by mouse lethality test a percentage (31%) and 16 isolate showing positive to tox A by using PMT-ELISA a percentage (44.4%).PCR was used to detect tox A gene and showed that 16 isolates were positive for tox A gene. Multiplex PCR by using amplified DNA showed that all toxigenic isolates of P. multocida were capsular type A. DNA nucleotide sequencing and analysis of sequences obtained for the tox A gene under investigation observed that: P. multocida isolates had no genetic diversity for tox A gene among small and large ruminants and the identity between 2 isolate 99.6% to 100%.