The biochemical characteristics and antibiotic susceptibility of 12 Ornithobacterium rhinotracheale strains isolated from chickens and turkeys suffering from respiratory clinical signs and the survival of some isolates on egg-shell and within chicken eggs during hatching were examined. All O. rhinotracheale strains showed typical biochemical characteristics. Among the 16 drugs examined, penicillin G, ampicillin (MICs ranging from < or = 0.06 microgram/ml to 1 microgram/ml), ceftazidim (with MICs from < or = 0.06 microgram/ml to 0.12 microgram/ml), erythromycin, tylosin, tilmicosin (with some exceptions MICs ranged from < or = 0.06 microgram/ml to 1 microgram/ml) and tiamulin (MICs varied from < or = 0.06 microgram/ml to 2 micrograms/ml) were the most effective. Lincomycin, oxytetracycline and enrofloxacin also gave good inhibitions, but with most strains in a higher concentration (MICs ranged in most cases from 2 micrograms/ml to 8 micrograms/ml). The other antibiotics inhibited the growth of O. rhinotracheale only in very high concentrations (colistin) or not at all (apramycin, spectinomycin, polymyxin B). At 37 degrees C, O. rhinotracheale did not survive on egg-shell for more than 24 hours, while upon inoculation into embryonated chicken eggs it killed embryos by the ninth day, and from the 14th day post-inoculation no O. rhinotracheale could be cultured from the eggs at all. These results suggest that O. rhinotracheale is not transmitted via eggs during hatching.