Attempts to Demonstrate a Surface Antigen of Staphylococci and Specific Phagocytosis

Abstract

Lyons 1 has recently reported the results of his studies on antibacterial immunity to the staphylococcus. He states that young infusion-broth cultures of toxigenic and non-toxigenic strains of staphylococci are encapsulated; old infusion-cultures contain mostly non-encapsulated cocci; the capsule is not present in young serum-grown cultures; capsules are no longer demonstrable after agitation on a mechanical shaker, but they withstand heating to 100°C for 5 minutes; young (2-hour) broth cultures when exposed to defibrinated blood are only phagocyted in small numbers in 15 minutes, as compared to overnight cultures which are phagocyted in large numbers. In other words, the young encapsulated cocci are resistant to phagocytosis. Lyons indicates that a marked phagocytosis of a young culture is related to a specific factor present in serum. It should also be pointed out that he has reported type-specific agglutinins present in the serum of rabbits immunized with young cultures, whereas immunization with old cultures resulted in a preponderance of group-agglutinins. No swelling of the capsules (“Quellung”) could be demonstrated in young encapsulated organisms when added to this type-specific serum.

Because little is known concerning antibacterial immunity in patients with staphylococcal sepsis, it appeared highly important to extend the observations of Lyons as to whether young cultures of staphylococci isolated from patients possessed a capsule that could be demonstrated morphologically, and whether these young organisms resisted phagocytosis. In the present study, attempts were made to demonstrate an encapsulated phase of several strains of staphylococci. Quantitative phagocytic studies were also carried out with the use of human leukocytes and young and old cultures of staphylococci. Thirty strains of pathogenic staphylococci were used; 27 of which were isolated from patients, and 3 were supplied to us by Dr. A. T. Henrici of the Department of Bacteriology, University of Minnesota.