Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms

Avian pathogenic Escherichia coli (APEC) causes severe colibacillosis in poultry. This study compared the efficacy of the third-generation fluoroquinolone levofloxacin and the second generation enrofloxacin against APEC. In vitro, 155 samples from broiler farms in Qalyubia, Egypt, yielded 43 E. coli isolates, with 16 forming strong biofilms. Antibacterial sensitivity testing revealed levofloxacin had a higher susceptibility rate (43.75%) and larger inhibition zones (26 mm) compared to enrofloxacin (18.75%, 13 mm). Levofloxacin demonstrated superior antibacterial activity compared to enrofloxacin (13 mm). In vivo, 150 broiler chicks were experimentally infected with a common APEC O2 strain and divided into negative control, positive control, levofloxacin-treated, enrofloxacin-treated, and enrofloxacin and colistin combination groups. Levofloxacin treatment resulted in significantly higher body weight gain, lower mortality (3.33% vs. 6.67%), and improved feed conversion ratio compared to enrofloxacin. It also produced better hematological and biochemical profiles, reduced oxidative stress markers (MDA, SOD, GSH), and achieved lower bacterial counts in organs posttreatment. The results conclusively demonstrate that levofloxacin is more effective than enrofloxacin in treating colibacillosis, offering enhanced performance, health outcomes, and microbiological clearance in broiler chickens.