Acinetobacter baumannii bloodstream infection while receiving tigecycline: a cautionary report.
OBJECTIVE
Tigecycline has shown in vitro activity against Acinetobacter baumannii. Yet, published clinical experience with tigecycline use outside clinical trials is lacking. We describe, for the first time, bloodstream infection caused by tigecycline-non-susceptible A. baumannii occurring in patients receiving tigecycline for other indications. The possible mechanisms of resistance and pharmacokinetic limitations of the drug are addressed.


METHODS
The clinical records of involved patients were systematically reviewed. Tigecycline susceptibility testing was initially performed using the Etest method and confirmed by agar dilution. Involved isolates underwent PFGE and exposure to phenyl-arginine-beta-naphthylamide (PAbetaN), an efflux pump inhibitor.


RESULTS
Two patients developed A. baumannii bloodstream infection while receiving tigecycline. Tigecycline was administered for other indications for 9 and 16 days, respectively, before the onset of A. baumannii infection. Patient 1 died of overwhelming A. baumannii infection and Patient 2 recovered after a change in antibiotic therapy. The MICs of tigecycline were 4 and 16 mg/L, respectively. Both isolates had a multidrug-resistant phenotype and were genotypically unrelated. After exposure to PAbetaN, the MICs reduced to 1 and 4 mg/L, respectively.


CONCLUSIONS
To our knowledge, this is the first clinical description of bloodstream infection caused by tigecycline-non-susceptible A. baumannii. Such resistance appears to be at least partly attributable to an efflux pump mechanism. Given the reported low serum tigecycline levels, we urge caution when using this drug for treatment of A. baumannii bloodstream infection.
Peleg
Anton Y
AY
Division of Infectious Diseases, University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA.
Potoski
Brian A
BA
Rea
Rhonda
R
Adams
Jennifer
J
Sethi
Jigme
J
Capitano
Blair
B
Husain
Shahid
S
Kwak
Eun J
EJ
Bhat
Sunil V
SV
Paterson
David L
DL
D040981:Acinetobacter baumannii / Q000187:drug effects*; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy*; D004151:Dipeptides / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008911:Minocycline / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D000078304:Tigecycline
D000900:Anti-Bacterial Agents; D004151:Dipeptides; C419365:phenylalanine arginine beta-naphthylamide; D000078304:Tigecycline; D008911:Minocycline