Antibiotic sensitivity and resistance in Ornithobacterium rhinotracheale strains from Belgian broiler chickens

Establishing the antibiotic sensitivity of the avian respiratory pathogen O rnithobacterium rhinotracheale is difficult because of the organism's compl ex growth requirements and the unusually frequent occurrence of resistance. The minimal inhibitory concentrations of 10 antibiotics were determined fo r 45 strains of O. rhinotracheale from Belgian broiler chickens collected f rom 45 farms between 1995 and 1998. They were compared with the type strain , which was isolated from a turkey, and a strain isolated from a rook. All the broiler strains were resistant to lincomycin and to the beta -lactams a mpicillin and ceftiofur. Less than 10% of the strains were sensitive to the macrolides tylosin and spiramycin, tilmicosin and flumequine. A few strain s were sensitive to enrofloxacin and doxycycline. All strains were sensitiv e to tiamulin.