Biofilm Formation Restrained by Subinhibitory Concentrations of Tigecyclin in Acinetobacter baumannii Is Associated with Downregulation of Efflux Pumps.
BACKGROUND
Tigecycline, one of the few therapeutic options against multidrug-resistant Acinetobacter baumannii, reaches subinhibitory serum concentrations only with cautious clinical dosing and pharmacokinetics. Subinhibitory concentrations of tigecycline might induce an A. baumannii biofilm.


METHODS
Biofilm formation was assessed via the crystal violet staining method. We further analyzed the main biofilm components with NaIO4, proteinase K, and DNase. Real-time RT-PCR was applied for quantitative detection of biofilm potential-associated genes.


RESULTS
In this study, A. baumannii proved to be a strong biofilm producer, and we found that proteins and extracellular DNA are crucial components of the A. baumannii biofilm. Quantitative real-time RT-PCR revealed positive correlations between biofilm formation restrained by subinhibitory concentrations of tigecycline and the expression of biofilm potential-associated genes, especially the AdeFGH efflux pump gene.


CONCLUSIONS
Our results suggest that downregulation of efflux pumps, especially the AdeFGH efflux pump, is probably responsible for the decline in biofilm formation in A. baumannii treated with subinhibitory concentrations of tigecyclin.
Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
Huale
H
Chen
Jianming
J
Cao
Cui
C
Zhou
Haiyang
H
Liu
Xiaoxiao
X
Zhang
Tieli
T
Zhou
D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000502:physiology; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D015536:Down-Regulation / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008826:Microbial Sensitivity Tests / Q000379:methods; D008911:Minocycline / Q000008:administration & dosage / Q000031:analogs & derivatives*; D000078304:Tigecycline
D000900:Anti-Bacterial Agents; D026901:Membrane Transport Proteins; D000078304:Tigecycline; D008911:Minocycline