الفهرس 
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Abstract
This work was conducted on 55O growing chicks from which 380 of the lohman and Habard breeds, 170 of Dokki breed collected from the different governmental poultry farms at Assiut governorate. The chicks suffered from leg affections particularly at the area of the hock joint,
- Complete bacteriological examination revealed positive bacterial isolation only from 89 chicks out of 360 of the lohman and Habard breeds.
It was possible to isolate various microbes from the hock joint region. The most important of these microbes were: E. coli (23 isolates), staphylococcus aureus (10 isolate), Salmonella gallinarum pullorum (1 isolate) and pseudomonas aeuroginosa (5 isolates).
- The serotyping of the E. coli isolates, divided them into main five groups : O127 K63(B8) (2), O111 : K58(B4)(6), O114 K-(B-) (1), O124 K72 (B17) (3) and O25 : K11 (L) (1).
- The serological examination of the salmonella isolate showed that the antigenic structure was 1, 9, 121, 122, 123, hence classified as salmonella gallinerum- pullorum.
Experimental infection in 4 weeks old Habard chicks for the different isolated microbes revealed that:-
- The pathogenicity of staphylococcus aureus isolate in growing chickens reached 100 % either through intravenous or foot pat routes.
- E. coli serotype O111: K58(B4) was very pathogenic, O124 K72 (B17) and O127 K63 (B8) were moderately pathogenic, O25: K11 (L) was weakly pathogenic an O114 -K-(B-) was nonpathogenic.
- The pathogenicity of S. gallinarum pullorum reached 80% in case of foot pad inoculation. 4/5 of the birds showed swollen foot pad. In the i/v route of inoculation the pathogenicity reached only 60 % joint infection.
- The pseudomonas aeuroginosa appeared less pathogenic to infect the joint in comparison with staphylococcus aureus and Salmonella gallinerum- pullorum organisms.
The isolated microorganisms were tested in vitro against different antimicrobial agents. The result of these tests revealed that the Josamycin, Lincomycin and erythromycin were sensitive to all tested microorganisms but pseudomonas aeuroginosa resisted many of the used antimicrobial agents.