High tigecycline resistance in multidrug-resistant Acinetobacter baumannii.
OBJECTIVE
Multidrug-resistant (MDR) Acinetobacter baumannii is increasing in our hospital and worldwide, raising the necessity of finding effective therapies. We aimed to evaluate the in vitro activity of tigecycline against MDR A. baumannii clones isolated before tigecycline was used in our institution.


METHODS
Eighty-two unique patient clinical isolates of multidrug-resistant A. baumannii collected in 2003 were studied. Species identification and antibiotic susceptibilities were determined by Vitek-2. Tigecycline MIC was determined by Etest. Clonal relatedness was determined by PFGE.


RESULTS
MDR A. baumannii possessed 19 different pulsotypes. Sixty-six percent of the isolates were resistant to tigecycline, 12% were intermediate and 22% were susceptible. The MIC(50) and MIC(90) of tigecycline were 16 and 32 mg/L, respectively, with a wide MIC range of 1-128 mg/L. Variability in MIC of tigecycline was evident between and within the same pulsotype.


CONCLUSIONS
We report here high resistance rates to tigecycline, and higher than previously described MICs, in multiple clones of MDR A. baumannii. As tigecycline represents a new treatment choice for infections caused by A. baumannii, these findings are worrisome.
Navon-Venezia
Shiri
S
The Laboratory for Molecular Epidemiology and Antibiotic Research, Department of Epidemiology, Tel Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. shiri_nv@tasmc.health.gov.il
Leavitt
Azita
A
Carmeli
Yehuda
Y
D000151:Acinetobacter Infections / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D013753:Tetracycline Resistance; D000078304:Tigecycline
D000900:Anti-Bacterial Agents; D000078304:Tigecycline; D008911:Minocycline