Further Studies on Mechanism of Invasiveness by Pyogenic Bacteria

Abstract

The writer has recently demonstrated that the dissemination of a foreign substance from its site of inoculation is at least in part a function of its irritating capacity. 1 , 2 Staphylococcus aureus induces a lesion sufficiently intense to occlude draining lymphatics and to cause the formation of a fibrinous network as early as one hour after cutaneous inoculation of the organism. The degree of “walling-off” was determined by studying the dissemination of trypan blue from the site of injury to the regional lymphatics. In the case of Type I pneumococcus the area is circumscribed at a somewhat later stage (about 6 hours subsequent to the inoculation of the organism). When Streptococcus hemolyticus is inoculated into the skin the lymphatics maintain their functional patency for about 2 days, and throughout that time these vessels are virtually unoc-cluded by thrombi. This histological observation adequately accounts for the delayed fixation and consequently the relative ease with which the dye penetrates to the regional lymphatics in a hemolytic streptococcal inflammation.

These results, while offering an explanation for the well-known localizing tendencies of the staphylococcus as against the disseminating properties of streptococcus, present an interesting paradox. Staphylococci tend to remain localized and produce relatively slight systemic effects because of their pronounced local injurious action which serve to fix them in situ. Hemolytic streptococci, on the contrary, produce far greater systemic sequelae owing to the invasiveness resulting from their relatively mild local effects.

The experiments of the writer have recently been confirmed by Dennis and Berberian. 3 Subsequent to the writer's observations, Tillett and Garner 4 have demonstrated that broth cultures of hemolytic streptococci are capable of liquefying the normal human fibrin clot. In contrast to this they pointed out that the normal rabbit fibrin clot is totally resistant to dissolution by such means.