Local microbial tolerance was investigated in a murine model of peritonitis. Peritoneal bacterial burden and inflammatory cytokine concentrations were determined at different times, within 48h after infection. Peritoneal macrophages were harvested from naïve mice or from mice 48h after infection and underwent ex vivo stimulation with different concentrations of Klebsiella. Cytokine secretion was determined in the supernatants. Peritoneal bacteria concentrations, remained relatively steady between 24h (median: 5.04 log CFU) and 48h (median: 5.19 log CFU) after infection. Peritoneal cytokine concentrations peaked early but were already diminished at 48h after infection, despite persistent high bacteria levels. Macrophages, harvested from naïve mice responded vigorously to ex vivo stimulation with 10(5) CFU and 2 x 10(8) CFU Klebsiella. Cells harvested from animals 48h after infection, were unresponsive to an ex vivo stimulation with 10(5) CFU Klebsiella, but fully responded to 10(8) CFU. Persistent intraabdominal bacterial infection induced dose dependent microbial tolerance in peritoneal macrophages.