Abstract

HeaThe present study was carried out to isolate and identify the bacterial agents involved in field cases of avian cellulitis in broiler chickens and also to examine isolated bacteria for antibiotic susceptibility. The study was applied on 290 broiler chickens, aged 30-35 days, suffered from cellulitis (65 with head and 225 body lesions) to isolate bacterial agents. All obtained isolates were identified and tested for the pathogenicity based on Congo red assay. Disc diffusion test was used to study the sensitivity pattern of bacterial isolates with determination of multiple antibiotic resistance index. Results revealed that all head and 91.5% of body samples were positive on bacteriological examination. E. coli was the most prevalent isolate (45.2%), followed by staphylococci (33.2%), Clostridia (5.4%), streptococci (5.1%), Proteus mirabilis (4.4%), Enterobacter spp. (3.2%), Pseudomonas aeruginosa (2.2%), and Aeromonas spp. (1.2%). Congo red binding test was positive for P. aeruginosa (100%), Clostridia (72.7%), E. coli (65.8%), staphylococci (62.2%), Aeromonas spp. (60%), P. mirabilis (38.9%), Enterobacter spp. (38.5%) and streptococci (33.3%). Serological typing of E. coli identified nine O serotypes, with high predominance of O78 (19%). On antibiotic susceptibility profiling, E. coli isolates demonstrated 83.1-92.9% resistance to chloramphenicol, tetracycline, and enrofloxacin. Staphylococci isolates showed high resistance to ampicillin (97.0%) and clindamycin (82.9%). Clostridial and Aeromonas spp. isolates showed 100% resistant to tetracycline, enrofloxacin, and cefotaxime. Enterobacter spp. showed 100% resistance to chloramphenicol and cefotaxime. P. aeruginosa had 100% resistance to tetracycline and enrofloxacin. Also, streptococci isolates showed 100% resistance to erythromycin. Totally, 56.3% bacterial isolates were multidrug-resistant, 23.8% extensively drug-resistant and 1.5% pan drug-resistant. The present study concluded that E. coli is the most predominant pathogen involved in cellulitis, particularly O78 serotype. In addition, this study demonstrated high prevalence of multidrug-resistant bacteria among isolates, particularly against commonly used antibiotics. Therefore, it is recommended to use antibiotic sensitivity tests and accurate therapeutic doses to efficiently treat and control bacterial infections in poultry.