In vitro antibiotic resistance profiles of Ornithobacterium rhinotracheale isolates from commercial chickens submitted to Razi institute in 3 different times (2000, 2001 & 2007)

Ornithobacterium rhinotracheale (ORT) is one of the causes of poultry respiratory diseases. In this study in vitro drug sensitivity of 47 ORT isolates using standard disk diffusion were examined with 35 different antibiotics. The isolates originating from commercial chicken flocks submitted in 2000, 2001 and 2007 to Razi institute. None of the isolates was resistant to tiamulin , and less than 50% were resistant against ampicillin , amoxycillin , imipenem , doxycyclin, tylosin ,cefalexin, penicillin, ciprofloxacin, norfloxacin, ticarcillin, chloramphenicol, danofloxacin, florphenicol, ceftiofur, furazolidone and clindamaycin. All the isolates were completely resistant to colistin, erythromycin, gentamicin, co-trimoxazole, sultrim, lincomycin, nafcillin and neomycin. There were antibiotic resistance increase in 2007 isolates compared with 2000 and 2001 in several antibiotics including streptomycin, tetracycline, oxytetracycline, chlortetracycline, ticarcillin, ceftiofur, furazolidone, penicillin, danofloxacin, cefalexin, and linco-spectin. In others no change or even resistance decrease were seen. Of course because of different geographic area and different breeds of birds this comparison cannot be generalized. Because of acquired antibiotic resistance, and various results of antibiotic therapy, it must be stressed to ORT antibiogram test more than before.