Summary :Danofloxacin is recent antibacterial agent belong to the fluoro- quinolone family and is active against Gram-ve enterobacteria species. Ceftiofur sodium is a third-generation cephalosporin against Gram-ve and Gram+ ve and anaerobic pathogens.E.coli infection in chickens has been in the last decade a major problem in poultryfarms all over the world.The present study was performed to investigate the effect of danofloxacin (5mg /kg b. wt in drinking water) or ceftiofur sodium (2mg/ kg b. wt s/c) for three successive days on treatment of infected chicks with E.coli as well as on haemogram and some biocΙ-Antibacterial activity in vitro:The present investigation showed that MIC of danofloxacin was 0.6 µg/ml against E.coli and MIC of ceftiofur sodium was 0.2 µg/ml against E.coli .Sensitivity of E.coli pathogenic strains of avian origin to commercial discs namely danofloxacin, ceftiofur sodium , enrofloxacin, gentamicin, oxytetracyclin, chloramphenicol, ciprofloxacin, suphonamide with trimethoprime were measured. The results revealII – Antibacterial activity in vivo:A total number of 120 one day old chicks were classified into 6 equal groups, each of 20 chicks1st group Non-infected non treated (Healthy control)2nd group Non-infected treated with danofloxacin (5mg /kg b. wt in drinking water) for three successive days3rd group Non-infected treated with ceftiofur sodium (2mg/ kg b. wt s/c) for three successive days4th group Infected non treated (Infected control )5th group Infected treated with treated with danofloxacin (5mg /kg b. wt in drinking water) for three successive days6th group Infected treated with ceftiofur sodium (2mg/ kg b. wt s/c) for three successive daysBlood samples were taken at the end of 1st day, 7th day and 14th post-treatment for haematological studies and another blood samples were collected to separate serum for investigation of some biochemical parameters.1-Clinical symptoms:Normal chicks (non-infected non treated) and also infected treated with danofloxacin or ceftiofur sodium were healthy, viable showing no clinical symptoms along the course of the experiment. whereas E.coli infected and non-medicated group displayed clinicAdministration of danofloxacin or ceftiofur sodium to E.coli infected broiler chicks improved disease symptoms and completely disappeared at 7th day post treatment.2- Mortality rate:The mortality rate was zero in the groups non infected medicated with danofloxacin or ceftiofur sodium and group non infected non treated.Experimental infection with E.coli evoked high mortality rate (25 %) whereas group infected with E.coli medicated with danofloxacin or ceftiofur sodium reduced the mortality rate to 5 %.3- Lesion scores:2- On other hand, enterococci mean count was 5.0x105, 26.0x104 and 7.1x104 in the examined raw milk, kariesh and processed cheeses samples. Enterococcus faecalis mean count was 24.0x104, 41.0x104 and 41.0x104 in the examined samples, respectively. While, 3- The total aerobic spore formers mean count in the examined raw milk, kariesh and processed cheeses samples was 45.0x104, 6.9x105 and 36.0x105, respectively. In raw milk,13 isolates were identified as 7 aerobic spore formers, Bacillus cereus (7.7%), BacThe sanitary and public health importance for isolated microorganisms as well as their control measures were discussed to improve the quality of raw milk, kariesh and processed cheeses to safe guard the consumers from infection.