Isolation of toxigenic strains of Pasteurella multocida from lungs of pneumonic swine.

Lungs from 113 pneumonic pigs were examined for Pasteurella multocida. The lungs were smeared directly onto blood agar and homogenized in brain-heart infusion broth and then inoculated intraperitoneally in mice. Pasteurella multocida isolates were typed for serotypes A (by hyaluronidase inhibition of capsule) and D (by acriflavine autoagglutination). Strains were tested for toxin production by intradermal injection of 0.2 ml of filtered 24-hour culture supernatants into guinea pigs. Most lungs (70.8%) yielded isolations. Most isolants (87.5%) were type A and 12.5% were type D. Of the type D strains, 80% were toxigenic. Of the type A isolants, 18.2% were toxigenic.