Tigecycline Evaluation Surveillance Trial (TEST) in vitro antibacterial activity against selected species of Enterobacteriaceae in the United States
Abstract number: 1134_02_4
Bouchillon S., Stevens T., Johnson B., Johnson J., Hoban D., Hackel M., Person M., Dowzicky M.
Tigecycline, a member of a new class of antimicrobials (glycylcyclines), has been shown to have a potent expanded broad spectrum activity against most species of Enterobacteriaceae as well as gram-positive, atypicals and anaerobes. The TEST program determined the in vitro activity of tigecycline compared to amikacin, ampicillin, imipenem, cefepime, ceftazidime, ceftriaxone, levofloxacin, minocycline and piperacillin/tazobactam against isolates of Enterobacteriaceae collected from hospitals across the USA.
A total of 2446 clinical isolates, collected in 2004, were identified to the species level at each participating site and confirmed by the central laboratory. Minimum Inhibitory Concentration (MICs) were determined by the local laboratory using broth microdilution panels and interpreted according to NCCLS guidelines.
The efficacy of all broad spectrum antimicrobial agents still remain highly active against Enterobacteriaceae in the United States. The susceptibility rates for amikacin, cefepime, ceftazidime, ceftriaxone, imipenem, levofloxacin, minocycline and piperacillin/tazabactam are 99.3%, 97.5%, 89%, 92.2%, 98.8%, 85.5%, 85.7% and 91.8%, respectively. Tigecycline's activity was similar to imipenem presenting a MIC50/MIC90 of 0.25/1 mcg/ml against all strains of Enterobacteriaceae. The frequency of ESBL production among K. pneumoniae and E. coli was found to be 8.5% and 2.2%, respectively. Tigecycline successfully inhibited >98% of all E. coli and K. pneumoniae ESBL producers at a MIC of 2 mcg/ml. It was also noticed unusual resistance to imipenem in 29 of these isolates. While still under more detailed analysis, preliminary data have shown that tigecycline presented a MIC50/MIC90 of 1/2 mcg/ml against these multi-resistant isolates.
Most of broad spectrum antimicrobial agents still remain active against Enterobacteriaceae from the US. Tigecycline's activity was comparable to the activities of broad spectrum antimicrobials and with greater activity against most ESBL and AmpC producing isolates. Tigecycline also showed in vitro activity against isolates that were intermediate or resistant to imipenem, which in many instances is considered as a last therapeutic option. The presented data suggest that tigecycline may be an effective and reliable therapeutic option against both susceptible strains of Enterobacterieaceae and multi-drug resistant strains regardless of degree or type of resistance.
|Session name:||XXIst ISTH Congress|
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