Efficacy of broth-grown Pasteurella multocida bacterins in ducklings

Pasteurella multocida (PM) isolates produced dense growth in tryptic soy broth and modified tryptose broth (MTB) when the media were continuously shaken or aerated. In carboys containing 15 liters of aerated MTB, the growth exceeded an absorbance of 0.9 and contained about 10(10) colony-forming units per ml. Bacterins prepared from PM isolates grown in MTB were injected subcutaneously into ducklings at 2 and 3 weeks of age. Such ducklings experienced significantly less mortality than unimmunized controls following homologous challenge at 4, 5, or 6 weeks of age. Similar protection was provided against challenge by a heterologous isolate (same serotype). Six-week-old ducklings given a single injection of an oil-emulsified PM bacterin developed immunity that lasted for 8 weeks.