Show lack of improvement or worsening in signs and symptoms of infection, including continued or worsening peritoneal findings Require additional surgical intervention which must be performed within 24 hours of first dose of study medication with no more than one pre-surgical dose of an antibiotic given for pre-operative prophylaxis AND/OR Be post-op and have required surgery within 24 hours prior to first dose of study medication with no more than one pre-surgical dose of an antibiotic given for pre-operative prophylaxis.