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Antimicrob Agents Chemother. 2013 Oct;57(10):4831-40. doi: 10.1128/AAC.00865-13. Epub 2013 Jul 22.

Unique structural modifications are present in the lipopolysaccharide from colistin-resistant strains of Acinetobacter baumannii.

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1
Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland, USA.

Abstract

Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause severe infections, including hospital-acquired pneumonia, wound infections, and sepsis. Multidrug-resistant (MDR) strains are prevalent, further complicating patient treatment. Due to the increase in MDR strains, the cationic antimicrobial peptide colistin has been used to treat A. baumannii infections. Colistin-resistant strains of A. baumannii with alterations to the lipid A component of lipopolysaccharide (LPS) have been reported; specifically, the lipid A structure was shown to be hepta-acylated with a phosphoethanolamine (pEtN) modification present on one of the terminal phosphate residues. Using a tandem mass spectrometry platform, we provide definitive evidence that the lipid A isolated from colistin-resistant A. baumannii MAC204 LPS contains a novel structure corresponding to a diphosphoryl hepta-acylated lipid A structure with both pEtN and galactosamine (GalN) modifications. To correlate our structural studies with clinically relevant samples, we characterized colistin-susceptible and -resistant isolates obtained from patients. These results demonstrated that the clinical colistin-resistant isolate had the same pEtN and GalN modifications as those seen in the laboratory-adapted A. baumannii strain MAC204. In summary, this work has shown complete structure characterization including the accurate assignment of acylation, phosphorylation, and glycosylation of lipid A from A. baumannii, which are important for resistance to colistin.

PMID:
23877686
PMCID:
PMC3811424
DOI:
10.1128/AAC.00865-13
[Indexed for MEDLINE]
Free PMC Article
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