MIGRATION OF RAT PERITONEAL-CELLS AFTER INTRAABDOMINAL INFECTION WITHBACTEROIDES-FRAGILIS AND ESCHERICHIA-COLI

A fibrin clot model for intra-abdominal abscess formation was used to study the migratory properties of peritoneal cells from rats during th e early stages of infection. Peritoneal cells and fibrin clot remnant were harvested 6 h after implantation of a sterile, singly infected (E scherichia coli or Bacteroides fragilis) or mixed infected (E. coli an d B. fragilis) fibrin clot. Histological study of fibrin clots, remove d 6 h after implantation, showed a deeper infiltration by host cells o f B. fragilis infected clots compared to the others. This difference i n infiltration by peritoneal cells was not due to differences in fibri nolytic activity of the bacterial strains. Differential cell counts of the peritoneal cells from rats implanted with sterile, singly and mix ed infected fibrin clots showed distribution over subpopulations to be independent of the bacterial content of the infected clots used. In v itro migration assays showed no significant differences in migration b y peritoneal cells from rats implanted with clots containing a differe nt bacterial composition. Since B. fragilis infected fibrin clots were more deeply infiltrated by host defence cells than the other clots, a nd only mixed infected clots led to persistent abscesses in this model , we conclude that local conditions within the fibrin matrix rather th an intrinsic cellular capacities of the host cells are important for t he process of abscess formation.