الفهرس 
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Abstract
To study the virulence factors possessed by C. pseudotuberculosis causing CLA in sheep and OSD in buffaloes, 8 isolates were recurred from sheep showing CLA and 17 isolates recurred from buffaloes showing OSD. All isolates were biochemically identified. During this biochemical identification, 4 sheep isolates showed results which lead to suspecting to may be C. ulcerans. PLD production of all isolates was detected by synergistic hemolytic activity using Modified CAMP test. The pld gene in all isolates was assayed by PCR. The presence of C. ulcerans pld gene was determined by PCR using primers designed locally in all sheep and buffalo isolates. DT produced by C. pseudotuberculosis of sheep and buffalo isolates was determined by using Modified Elek test. Virulence of isolates having only pld p or both pld p and pld u genes was assay by S/C inoculation in guinea pigs, moreover, buffalo isolates that could produce DT in addition to one or both of pld p and pld u genes was assessed by inoculation in guinea pigs. The investigation revealed that the virulence of C. pseudotuberculosis is controlled by 3 factors the pld p, pld u genes and DT production.