Tigecycline activity tested against 26,474 bloodstream infection isolates: a collection from 6 continents

The activity of tigecycline (formerly GAR936), a novel glycylcycline, was tested against recent bloodstream infection (BSI) pathogen isolates from 6 continents. Frequency of clinical occurrence of these pathogens was determined and their antibiograms assessed using reference broth microdilution methods. A total of 26 474 strains were tested for tigecycline susceptibility according to the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) by the M7-A6 guidelines with interpretations from M100-S15 and the package insert. The rank order of pathogens was Staphylococcus aureus (33.1%), Escherichia coli (14.0%), coagulase-negative staphylococci (13.5%), Enterococcus spp. (12.3%), Klebsiella spp. (5.7%), Pseudomonas aeruginosa (4.2%), Enterobacter spp. (3.0%), β-hemolytic streptococci (2.9%), Streptococcus pneumoniae (2.3%), and viridans group streptococci (1.4%). Tigecycline exhibited a broader spectrum of activity against BSI isolates when compared to ciprofloxacin, tetracycline, aminoglycosides, and many β-lactams (imipenem). Tigecycline was highly active against most pathogens tested, including staphylococci (MIC90, 0.5 μg/mL), enterococci (MIC90, 0.25 μg/mL), streptococci (MIC90, ≤0.12 μg/mL), Escherichia coli (MIC90, 0.25 μg/mL), Klebsiella spp. (MIC90, 1 μg/mL), and Enterobacter spp. (MIC90, 2 μg/mL), but showed limited inhibition of Pseudomonas aeruginosa (MIC90, 16 μg/mL) and indole-positive or indole-negative Proteae (MIC90, 4-8 μg/mL). In summary, tigecycline exhibited a wide spectrum of antimicrobial potency versus BSI isolates collected worldwide. Serious infections in nosocomial environments should benefit from tigecycline use among the investigational phase 3 agents focused toward resistant strains.