الفهرس 
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Abstract
The collected 942 samples from 34 broiler chicken flocks aged and 221 hatchery samples for isolation of Coagulase negative staphylococcus (CoNS).
Positive flocks were 15 /34 (34.09%) including 69.23% diseased and 38.95% in apparent healthy. Twenty sex Staphylococcus isolates from 942 samples (2.77%) including 6 liver, 6 kidney, 6 intestine, 4 lung, 2 air-sacs and 2 nasal sinus with rate of 3.82%, 3.82%, 3.82%, 2.55%, 1.27% and 1.27%; respectively.
Hatchery samples reveals the isolation of 26 staphylococcus isolates (11.76%) including 12.96% from fertile eggs and 13.79% from dead in shell. Ten isolates were CoNS (38.46%). The obtained isolates were and represented 4.52% out of total samples including 15 S. xylosus, 5 S. scuiri and 2 S. scuiri. Eight S. xylosus was 6 (5.55%) from infertile eggs and 2 (2.29 %) from dead in shell, While the 2 S. scuiri. CoNS isolates showed 100% resistance to Oxytetracycline, Trimethoprime + Sulphamethexole, Calindamycin and Oxacillin. Susceptibility was 100% to Vancomycin and 90% to Enrofloxacin. Multidrug resistance was detected in 2 S.lentus, 5 S. scuiri and 15 S. xylosis; respectively.
The detected resistance gens gens are mecA tetK, blaZ , ermC, Kan , icaD in 90, 80, 60 , 90%, 30.0, 30.0 and 0; respectively.
One hundred and sixty, 1-day old broiler chicks were grouped into 4 equal groups, at the 10th day birds of groups 1- 3 were s.c inoculated with 0.5 ml containing y 1.5x 108 of S.xylosis, S.scuiri and S.lentus; respectively and group 4 was noninfected control.
Clinical signs in infected groups started at 2-3dpi as general signs. Signs disappear in Ciprofloxacillin treated subgroups 24 hr post treatment and lasted to the 7th day in non treated.
Average body weight gain in S.xylosis infected non treated was the highest (813.90 gm), followed by S. scuiri (778.50gm ) and 773.75 in S. lentus infected treated . FCR was the highest in control (1.69 treated) and (1.74 nontreated) followed by 1.92 in S.xylosis, S.scuiri infected treated and the lowest 1.94 was in S.lentus infected non treated. S. scuiri was reisolated from intestine and spleen (5th dpi) and from intestine (7 and 10 dpi). While S.lentus was reisolated from intestine , liver and spleen (3rd dpi) ; from intestine and spleen (5th dpi) and intestine (10th dpi).
Histopathological lesion was recorded infected in group as hemorrhages with sinusoidal dilation, focal areas of vacuolar degeneration , fatty degeneration and shrinkage of hepatocytes in liver, necrotic changes of lymphocytes and vacuolion of corpuscle in spleen. Leucocytic infiltration , degeneration and necrosis of epithelium surface and intraepithelial as well as submucosal leucoytic infiltration were seen in intestine.
In conclusion : Phynotypic and /or genotypic resistant multidrug CoNS were isolated from healthy , diseased flocks and hatchery . CoNS induce mild subclinical disease. Good hygiene is recommended in farms and hatchery , monitoring of CoNS as source for resistance genes and its impact on poultry industry and public health. Pathogenicity of CoNS in chickens needs more investigation.