Isolation and determination of antibiotic susceptibility of Ornithobacterium rhinotracheal (ORT) from broilers in Markazi province

Respiratory diseases cause significant damage to the poultry industry worldwide. In recent years, infection with Ornithobacterium rhinotracheal bacterium (ORT) has been reported frequently from different parts of the world, including Iran. The aim of current study was to isolate the causative agent and reveal the antibiotic susceptibility to common antibiotics. in Markazi province. In this study, twenty poultry farms reported with respiratory signs clinically were conducted to collect 231 samples including Lung, trachea and infraorbital sinus swaps from sick and dead birds in Markazi province during 2016-2017.The samples were cultured on blood agar medium with 5% sheep blood containing Gentamicin and Polymyxin B and then incubated with 7.5% CO2at 37 °C for 48 to 72 hours. The bacteria identification was carried out using biochemical and PCR tests. The antimicrobial susceptibility of the isolates to 15 common antibiotics which used in poultry farms was determined by Kirby &Bauer method as well. Fifteen ORT isolates out of the 20 farms (75%) were collected using biochemical and PCR methods. The results showed that the isolates were resistant to Enrofloxacin, Erythromycin, Penicillin, Amoxicillin, Colistin and Lincomycin completely(100%). These isolates also were mostly sensitive to Nitrofurantoin. The results of this study indicated that 15 out of 20 examined poultry farms in Markazi province had been infected with the Ornithobacterium rhinotracheale (ORT) and were highly resistant to common antibiotics.