RESUMEN
Sixteen adult horses were randomly divided into 4 equal groups (GI, GII, GIII and GIV) of 4 animals and each group was injected intraperitoneally with one of the following suspension:GI (100 x 10.000.000 colony-forming units (CFU) of Escherichia coli diluted in 500ml of 0.9 percent saline); GII (100 x 10.000.000 CFU of Bacteroides fragilis in 500ml of 0.9 percent saline); GIII (100 x 10.000.000 CFU of E. coli in combination with 100 x 10.000.000 CFU of B. fragilis in 500 ml of 0.9 percent saline); GIV (500ml of 0.9 percent saline). Abdominal wall sensitivity to external pressure and tension, diarrhea, decreased intestinal sounds and increased of heart rate were the clinical signs more frequently observed in inoculated horses. Horses inoculated with pure cultures of either E. coli or B. fragilis demonstrated mild and self-limiting peritonitis, while those inoculated with the combination of both bacteria demonstrated clinical signs of higher intensity and duration.