KINETICS OF KILLING LISTERIA-MONOCYTOGENES BY MACROPHAGES - RAPID KILLING ACCOMPANYING PHAGOCYTOSIS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 34  (2) , 131-141
Abstract
The kinetics of bactericidal activity of activated macrophages can be precisely described by a mathematical model in which phagocytosis, killing, digestion and release of degraded bacterial material are considered to occur continuously. To gain a better understanding of these events, the period of time between first contact of bacteria with macrophages and the onset of killing was determined. Activated rat peritoneal macrophages were incubated for various times up to 15 min with L. monocytogenes previously labeled with 3H-thymidine and the unassociated bacteria removed by 2 centrifugations through a density interface. Both cell-associated radioactivity and cell-associated viable bacteria, determined as colony forming units after sonication of the cell pellet, increased with time of incubation. The specific viability of these bacteria, expressed as the ratio of number of viable bacteria per unit radioactivity declined with time, as an approximate inverse exponential, after a lag period of 2.9 .+-. 0.8 min. Evidence is given that other possible causes for this decline in specific viability, other than death of the bacteria, such as preferential ingestion of dead Listeria, clumping of bacteria, variations in autolytic activity or release of Listericidins are unlikely. Thus, the activated macrophages kill Listeria .apprx. 3 min after the cell and the bacterium first make contact.