Tigecycline Activity when Tested against Bacterial Strains from United States Medical Centers: Variation in Potency and Spectrum since Approval for Clinical Use (2006-2012).
Antimicrob Agents Chemother. 2014 Feb 3;
Authors: Sader HS, Farrell DJ, Flamm RK, Jones RN
Tigecycline was initially approved by the United States Food and Drug Administration (USA-FDA) in June 2005. We assessed the evolution of tigecycline in vitro activity since the initial tigecycline approval for clinical use by analyzing the results of seven years (2006 - 2012) of the SENTRY Antimicrobial Surveillance Program in the USA. We also analyzed trends over time for key resistance phenotypes. The analyses include 68,608 unique clinical isolates collected from 29 medical centers and tested for susceptibility by reference broth microdilution methods. Tigecycline was highly active against gram-positive organisms with MIC50/90 values of 0.12/0.25 μg/ml for Staphylococcus aureus (28,278 strains; >99.9% susceptible), 0.06-0.12/0.12-0.25 μg/ml for enterococci (99.3-99.6% susceptible) and ≤0.03/≤0.03-0.06 μg/ml for streptococci (99.9-100.0% susceptible). When tested against 20,457 Enterobacteriaceae strains, tigecycline MIC50/90 values were 0.25/1 μg/ml (98.3% susceptible; USA-FDA breakpoints). No trend toward increasing tigecycline resistance (non-susceptibility) was observed for any species/group during the study period. The prevalence of multidrug-resistant (MDR) and extended-drug resistant (XDR) Enterobacteriaceae increased from 4.4 and 0.5% in 2006 to 8.5 and 1.5% in 2012, respectively. In the same period of time, the prevalence of Escherichia coli and Klebsiella spp. with an extended-spectrum β-lactamase (ESBL) phenotype increased from 5.8 and 9.1% to 11.1 and 20.4%, respectively; whereas rates of meropenem-non-susceptible Klebsiella pneumoniae escalated from 2.2% in 2006 to 10.8% in 2012. The results of this investigation showed that tigecycline generally retained potent activity against clinically important organisms isolated in USA institutions, including MDR organism subsets of gram-positive and -negative pathogens.
PMID: 24492361 [PubMed - as supplied by publisher]