Additive effect of an immunomodulator and broad-spectrum antibiotic in fecal peritonitis

Abstract

We examined the effect of muramyl dipeptide (3 μg/g body weight) and a broad-spectrum antibiotic cefoxitin (15 mg/kg) on survival and systemic bacteremia in rats with peritonitis. When muramyl dipeptide given 24 hours prior to placement of the bacterial inoculum was combined with a single prophylactic dose of cefoxitin, survival was 100 percent (p < 0.001) and systemic bacteremia at 4 hours postinoculation was significantly decreased. Twenty-four hour pretreatment with either muramyl dipeptide alone or cefoxitin alone was associated with survival rates of 43 percent and 56 percent, respectively. When muramyl dipeptide was given with cefoxitin at the time of administration of the bacterial inoculum, no survival advantage was seen over the use of cefoxitin alone. There were no significant differences among groups in quantitative bacteremia at 24 hours postinoculation or in the number of intraabdominal abscesses. This study clearly demonstrates an additive effect of muramyl dipeptide pretreatment given with a prophylactic dose of cefoxitin in a human fecal peritonitis rat model.