Demonstration of cross-protection between Pasteurella multocida type A and Pasteurella haemolytica, serotype 1

Mice immunized with the potassium thiocyanate extract of Pasteurella haemolytica, serotype 1, were found to resist a challenge infection of P. multocida type A, thus demonstrating cross-protection. This finding was further supported by the finding that an antiserum directed against the potassium thiocyanate extract of P. haemolytica was bactericidal to P. multocida and vice versa.