Journal of Advances in Biology & Biotechnology

Background: Avian pathogenic E. coli (APEC) is responsible for colibacillosis, a multifactorial disease characterised by respiratory distress, septicaemia, pericarditis, perihepatitis, and other systemic lesions that result in considerable morbidity and mortality in broiler flocks worldwide.

Aim: This study aimed to investigate mortality trends, disease distribution, age-wise susceptibility, isolation and identification of Escherichia coli, and the gross and histopathological features of colibacillosis in chickens in and around Hyderabad.

Study Design, Place and Duration of Study: An observational study involving the pathological and bacteriological examination of poultry carcasses was conducted at the Department of Veterinary Pathology, College of Veterinary Science, Rajendranagar, Hyderabad, between July and December 2025.

Methodology: Carcasses of chickens from poultry farms were examined for gross and histopathological lesions. E. coli was isolated and identified using cultural and biochemical methods, including IMViC tests. Antimicrobial susceptibility was evaluated using the Kirby–Bauer disc diffusion technique.

Results: During the study period, colibacillosis was recorded in seven outbreaks comprising 156 cases, yielding a case prevalence of 20.55% and a mortality rate of 1.95%. The disease affected birds in all age groups. The highest mortality was observed in the 15–21-day age group (2.33%), followed by the 0–7-day and 8–14-day age groups (2.00% each), the 22–28-day age group (1.67%), and birds aged >29 days (1.33%). Grossly, affected birds showed congestion of the visceral organs, fibrinous pericarditis, perihepatitis, and polyserositis. The intestinal wall was thickened, with catarrhal exudate in the lumen. Histopathologically, liver sections revealed inflammatory cell infiltration, dilatation and congestion of the central vein, and fibrin deposition between hepatocytes. Intestinal sections showed enteritis characterised by heterophilic and lymphocytic infiltration of the mucosa, submucosa, and muscularis, together with degeneration and desquamation of the villi. Antimicrobial susceptibility testing of 32 E. coli isolates demonstrated the highest sensitivity to ceftriaxone (81.25%), followed by ciprofloxacin (68.75%) and cefotaxime (56.25%).

Conclusion: Colibacillosis remains an important cause of mortality in poultry. Ceftriaxone and ciprofloxacin showed greater in vitro activity against E. coli isolates, indicating their potential therapeutic relevance.