A total of 569 nonduplicate isolates recovered from patients with community-onset or hospital-onset intraabdominal infections (IAIs) from 2001 to 2006 were studied. These included 28 Staphylococcus aureus and 541 Gram-negative isolates (33.6% Escherichia coli, 29.0% Klebsiella pneumoniae, 8.1% Acinetobacter baumannii, and 6.3% Pseudomonas aeruginosa). Minimum inhibitory concentrations (MICs) of the isolates to moxifloxacin, imipenem, and ciprofloxacin were determined using the agar dilution method and to tigecycline using the broth microdilution method. Extended-spectrum beta-lactamase (ESBL) producers were found in 15.5% (29 out of 182) of E. coli, 15.3% (24 out of 157) of K. pneumoniae, and 15.4% (2 out of 13) of K. oxytoca isolates. More than 85% of Enterobacteriaceae were susceptible to moxifloxacin, but this percentage was lower among E. coli (78%). The percentage of E. coli (K. pneumoniae) isolates that were not susceptible to moxifloxacin was 6% (0%) in 2001, 39% (17%) in 2003, and 21% (14%) in 2006. Tigecycline exhibited good in vitro activities against all S. aureus and >95% of all Enterobacteriaceae tested. Among the 24 isolates of ESBL-producing K. pneumoniae, 4 had tigecycline MICs > or = 2 microg/ml. Eighty percent of A. baumannii isolates exhibited tigecycline MICs of < or = 2 microg/ml. This study found that moxifloxacin and tigecycline exhibited good in vitro activity against bacterial isolates causing IAIs.