Modulation of Cross-Protection Factor(s) of Avian Pasteurella multocida

Abstract
Cross-protection factor(s) (CPF) of P. multocida were maintained in vitro through at least 9 serial passages. Different growth media and temperatures enhanced or repressed the ability of P. multocida to produce CPF. Certain amino acids were innocuous to expression of CPF. B-vitamins enhanced CPF, whereas certain inorganic salts repressed CPF. The plasma of normal turkeys contained a compound or compounds responsible for expression and maintenance of CPF.