الفهرس 
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Abstract
Avian Mycoplasmosis is caused by several pathogenic mycoplasmas of which Mycoplasma gallisepticum (MG) and M. synoviae (MS) are the most important. It predisposes the birds to other infection yielding significant losses in performance and associated economics to all sectors of the poultry industry.
In this study:
1. The prevalence of of Mycoplasma infection in chickens from Sharkia and Al ismailia was studied. For this aim two hundred samples were collected.
2. Primary isolation of the microorganism on PPLO medium, which appeared as fried egg when examined by dissecting microscope.
3. Isolation of Mycoplasma from different sites(swabs &organs and swollen joints) yielded118 positive samples with a total incidence rate 59%. The highest recovery rate was from respiratory organs (72.7%) followed by swabs from nasal claft (46.7%) and samples from swollen joints (20%).
4. Application of Digitonin test for differentiation between Mycoplasma and Acholeplasma . Mycoplasma is digitoni positive while Acholeplasma is digitonin negative.
5. The incidence of Mycoplasma is 81.3% and the incidence of Acholeplasma is 18.6%.
6. Biochemical characterization of the obtained isolates gave 58 isolates suspected to be M. gallispectum from different sites of isolation with percentage of 49% and 18 isolates suspected to be M.gallinarium with percentage of 15.3% and 3 isolates suspected to be M.synoviae with percentage of 2.5% and 7 isolates suspected to be M.arginini with percentage of 5.9%.
7. Serological identification of isolates using specific antisera was applied which confirmed the presence of M. gallispectum and M.synoviae but not other genera (M.gallinarium and M.arginini) because of the lack of specific antisera .
8. In vitro susceptibility testing showed that the determination of minimum inhibitory concentration (MIC) values of some of antibiotics against Mycoplasma species.
9. Erythromycin and Tilmicosin was the most effective tested antibiotic (6) followed by Doxycycline and Tylosin (5) while Streptomycin (4) and Ciprofloxacin and Lincospectin (3) less effective against the tested isolates.
Summary
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10. Conventional PCR was adapted to confirm the presence of MG isolates using mgc2 and OIE primers which give a characteristic fragement at 300 and 185 bp respectively.
11. Conventional PCR was applied to confirm the isolation of MS from swollen joints using OIE primer which give a characteristic band at 205-210 bp.
12. Conventional PCR was applied to amplify the presence of un typed sharing the common gene for mycoplasma 23 ISR.
13. Sequence analysis of two mycoplasma gallisepticum for mgc2 gene and 16S r RNA gene from chicken revealed high similarity with the homologous reference strains on Gene Bank showing 100% identical with (Mycoplasma gallisepticum strain Nouh-C-15-mgC2 adhesion protein 2 (mgc2) gene, partial cds , Mycoplasma gallisepticum strain Eis-8-CK-14 cytadhesin protein 2 (mgc2) gene, partial cds and Mycoplasma gallisepticum strain Rab-E1-08- cytadherance- related surface protein (mgc2) gene, partial cds ).