Gram-positive bacteria-induced granulocytopenia and pulmonary leukostasis in rabbits

Abstract

Pneumococci have been shown to induce granulocytopenia and pulmonary leukostasis which might contribute to morbidity and mortality in pneumococcal sepsis. We studied whether other gram-positive species (groups A and B streptococci, Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens) could also induce these phenomena. Rabbits were challenged with nonviable preparations of each species, and all five species induced profound granulocytopenia (mean decrease of 90%) and pulmonary leukostasis. In vitro studies of serum incubated with these species of bacteria showed a mean consumption of total hemolytic complement of 90%, a mean increase of chemotactic activity for granulocytes of 204%, and a mean augmentation of granulocyte adherence of 45% (compared with 18% for the control). Infusion of sonicate-exposed sera induced granulocytopenia in recipient rabbits. Thus, several nonviable gram-positive species can interact with serum to activate the complement system, generate C5a bioactivity, augment granulocyte adherence, and generate a neutropenia-inducing factor. These alterations may contribute to granulocytopenia or pulmonary leukostasis, which may play a role in the morbidity and mortality associated with gram-positive bacterial infections.