Studies on Bacteriemia

Intravenous injection of staphylococci produced a marked, transient granulocytopenia inrabbits. Leukopenia was rapidly followed by return of polymorphonuclear leukocytes to the peripheral blood, and normal circulating granulocyte levels were reestablished within 20 to 40 minutes. Differential arterio-venous leukocyte studies showed that polymorphonuclear leukocytes were trapped within the pulmonary vascular bed and, less constantly, in the splanchnic viscera during the initial 10 to 20 minutes following the injection of staphylococci. Granulocytes were subsequently found in larger numbers in blood leaving the lungs and splanchnic tissues, suggesting that entrapped polymorphonuclear leukocytes rapidly reentered the blood stream. This sequence of changes in circulating granulocytes was not significantly altered by splenectomy or the administration of cortisone. It has previously been shown that virtually all staphylococci in the blood stream are found within circulating polymorphonuclear leukocytes 10 to 40 minutes after the injection of culture (9). It is during this period that granulocytes return to the blood stream in large numbers. These observations suggest that staphylococci are phagocyted by polymorphonuclear leucocytes temporarily sequestered in the lungs and splanchnic viscera. It appears probable that some sequestered granulocytes containing living staphylococci subsequently return to the circulation. Such intraleukocytic staphylococci are believed to play a role in the maintenance of bacteriemia.