摘要：E. coli infection in commercial broiler farms cause huge economic losses with relatively high mortality and production losses. This study was con- ducted to observe prevalence and identify patholog- ical lesions in E. coli infection in commercial broiler farms. along with determination of antibiotic re- sistance pattern. The samples total of 600 swabs from affected birds cloacal discharges and tissuesamples along with their data were collected from broiler farms and were then sent to Sindh Institute of Animal Health Karachi for analysis. The data was then recorded into a proforma regarding the location of farm and number of birds and age. A total number of 60 farms were examined out of which 31 farms were found to be positive, of which the high preva- lence were from Shahdadkot (90%), Larkana (90%) Thatta (80%), moderate were from Rohri (20%), Mirpurkhas (20%) whereas low prevalence were from Sukkur (10%). Among different forms of dis- ease, complex-form of infection had the highest prevalence (60%), followed by pericarditis (45%), omphalitis (40%), perihepatitis (36.6%), airsacculi- tis (33.3%), enteritis (31.6%) and coliseptecemia (21.6%). Prevalence of Colibacillosis was found to be higher in medium sized farms as compared to bothsmall and large farms, whereas for age it was found to be highest up to two weeks age. Histopathological lesions of these conditions included thick fibrous layer in the pericardium due to pericarditis, leuko-cyte infiltration and mvocardial degeneration, dila-tion of blood vessels due to congestion of liver andvacuolation in hepatocytes due to fatty degeneration in liver, fatty blunting and sloughing off villus in du- odenum, infiltration of lamina propria due to inflam- matory cells duodenum of broiler chick. For antibi- otic sensitivity of E. coli eleven antibiotics were ap- plied to check their sensitivity pattern. The isolates were highly sensitive to enrofloxacin (20%) and gemifloxacin (12.5%), moderately sensitive to doxycycline (32%), chloramphenicol (17.5%) and colistin (12.5%), and less sensitive to neomycin (42%), streptomycin (12.5%), gentamicin (12.5%) and penicillin (7.5%), while isolates were found to be resistant to tylosin (95%) and oxytetracycline (95%).
