The use of local and systemic antibiotics in rat fecal peritonitis

Treatment of fecal peritonitis includes administration of antibiotics, physical removal of contaminants, and restoration of gastrointestinal integrity. The temporal relationship of parenteral antibiotics and peritoneal irrigation with varied antibiotic solutions was studied in a peritonitis model. Antibiotics in high concentrations may actually inhibit host immune cells; therefore, dilute solutions used were MIC (minimum inhibitory concentration) (micrograms per millimeter) equivalent to usually achieved standard therapeutic blood levels. Sprague-Dawley rats were given a quantitative intraperitoneal challenge of 2 x 10(10) CFU/kg Escherichia coli and 10 mg autoclaved rat feces. Rats were randomized to receive 30 mg/kg intramuscular ceftriaxone (CTRX) either at the time of challenge (T = 0) or 2 hr later (T = 2). Two hours after peritonitis, rats received peritoneal irrigation with 30 cc of (1) normal saline, (2) dilute (10 mg/liter) CTRX solution, or (3) concentrated (1000 mg/liter) CTRX solution or (4) no irrigation. Survival and intraperitoneal pathology were then assessed. Parenteral CTRX given concurrently with peritoneal contamination improved survival (67%) compared with parenteral administration given 2 hr later (33%) (P < 0.05). Intraperitoneal CTRX irrigation improved survival (100%) in animals that received parenteral CTRX concurrently with contamination; this beneficial effect was present with both dilute and concentrated solutions and was significantly better than saline irrigation alone. Parenteral antibiotics given early after contamination of the peritoneum associated later with peritoneal lavage with antibiotic solutions improved survival.