Antibody response and protective ability of rabbits inoculated with Staphylococcus aureus strain CH-91.

Rabbits were inoculated subcutaneously with the protease-producing strain, CH-91, of Staphylococcus aureus of chicken origin. Dermatolysis was observed at the site of inoculation in them. Then the lesion outwardly healed up 5 to 6 weeks after the inoculation. When these recovered rabbits were reinoculated subcutaneously with the same number of viable cells as used in the first inoculation, none of them were affected with dermatolysis; that is, they had acquired a protective ability against an experimental challenge with viable cells. Antibodies against staphylococcal cells, alpha-hemolysin, and protease were detected in the serum of these rabbits 10 or 20 days after the first inoculation, but antibody against nuclease or beta-hemolysin was not. After the reinoculation, those antibodies showed a remarkable rise in most of the rabbits. These results suggest indirectly that the inoculated cells might have produced sufficient amounts of alpha-hemolysin and protease in the cutaneous tissue of rabbits. When rabbits were immunized with detoxicated culture supernatant of S. aureus strain CH-91, they exhibited antibody responses to alpha-hemolysin and protease mainly. Moreover, they were proved to have acquired a protective ability to an experimental challenge with viable cells when examined for the occurrence of dermatolysis as a marker of infection. On the contrary, when rabbits were immunized with killed cells, they presented a remarkable antibody response to staphylococcal cells. The immunized rabbits, however, acquired no protective ability.