Cross-Protection Studies with Pasteurella multocida Bacterins Prepared from Bacteria Propagated in Iron-Depleted Medium

Abstract

Strains X-73 (serotype 1) and P-1059 (serotype 3) of Pasteurella multocida, avian origin, expressed additional membrane proteins (MPs) when grown in brain-heart infusion (BHI) broth containing the iron chelator dipyridyl and when grown in BHI broth treated with the iron chelator Chelex 100. These additional MPs were not detected when both strains were grown in BHI broth. Chickens and turkeys were vaccinated twice with inactivated oil-emulsion vaccines containing bacterial cells expressing these MPs or with vaccines containing bacterial cells grown in BHI broth. Two weeks after the final vaccination, all birds were challenged to determine whether bacterins made from P. multocida that had been propagated in conditions of iron deprivation would induce heterologous serotype immunity. The bacterins produced in medium low in iron did not consistently induce significant protection against heterologous challenge.