Survey of bloodstream infections due to gram-negative bacilli: Frequency of occurrence and antimicrobial susceptibility of isolates collected in the United States, Canada, and Latin America for the SENTRY Antimicrobial Surveillance Program, 1997

During 1997, a total of 4,267 nosocomial and community-acquired bloodstream infections due to gram-negative organisms were reported from SENTRY hospit als in Canada (8 sites), the United States (30 sites), and Latin America (1 0 sites). Escherichia coli was the most common isolate (41% of all gram-neg ative isolates), followed by Klebsiella species (17.9%), Pseudomonas aerugi nosa (10.6%), and Enterobacter species (9.4%), For all gram-negative isolat es combined, the most active antimicrobials tested were meropenem, imipenem , and cefepime. The quinolones levofloxacin (MIC90, 2 mu g/mL), ciprofloxac in (MIC90, 1 mu g/mL), gatifloxacin (MIC90, 2 mu g/mL), sparfloxacin (MIC90 , 2 mu g/mL), and trovafloxacin (MIC90, 2 mu g/mL) were also active against most isolates. Bloodstream infection isolates from Latin America were unif ormly more resistant to all classes of antimicrobial agents tested than wer e isolates from Canada or the United States. Resistance phenotypes consiste nt with extended-spectrum p-lactamase production were also most common amon g E. coli and Klebsiella species from Latin America. Further investigation of the reasons for regional differences in resistance patterns is needed, a s is ongoing surveillance to detect resistance trends and to guide antimicr obial use.