Role of lymphatic vessels in bacterial clearance from early soft-tissue infection

T. G. DeLong and R. L. Simmons

A popular concept regarding the pathophysiologic characteristics of infection is that early bacterial clearance from tissue is an important host defense mechanism. Staphylococcus aureus, S epidermidis, Escherichia coli, enterococcus, and Klebsiella pneumoniae were radiolabeled with tritiated thymidine and injected subcutaneously into rabbit ears. Negligible clearance occurred at five hours, and less than 30% of injected bacteria cleared in 24 hours. Lymphatic function measured by clearance with bovine serum albumin labeled with iodine 125 was normal at all times during the first 24 hours. Clearance of live S aureus, radiolabeled by tritiated thymidine, was not accelerated by preexisting 12- or 24-hour hold-old inflammatory lesions. Clearance of bacteria rendered nonviable in vitro by antibiotics and heat were cleared in proportion to the degree of bacterial cell lysis. Bacterial clearance of S aureus correlated with the rate of bacterial lysis by polymorphonuclear leukocytes in vitro. These data support the hypothesis that lymphatic clearance of bacteria from soft tissues is of negligible importance as a host defense mechanism in the decisive period of soft-tissue infection.