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

Mark R Pelletier1, Leila G Casella, Jace W Jones

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

Antimicrobial Agents and Chemotherapy
|July 24, 2013
PubMed

Insights

Multidrug-resistant Acinetobacter baumannii develops colistin resistance through novel lipid A modifications, including galactosamine (GalN) and phosphoethanolamine (pEtN) additions. These structural changes are crucial for evading this last-resort antibiotic treatment.

Area of Science:

  • Microbiology
  • Structural Biology
  • Drug Resistance

Background:

  • Acinetobacter baumannii is a significant cause of hospital-acquired infections.
  • Multidrug resistance (MDR) in A. baumannii necessitates alternative treatment strategies.
  • Colistin is a critical antibiotic for treating MDR A. baumannii infections.

Purpose of the Study:

  • To elucidate the complete structure of lipid A in colistin-resistant A. baumannii.
  • To identify novel modifications contributing to colistin resistance.
  • To correlate laboratory findings with clinical isolates.

Main Methods:

  • Tandem mass spectrometry was employed for definitive structural analysis of lipid A.
  • Lipid A was isolated from both laboratory strains and clinical isolates of A. baumannii.
  • Structural characterization focused on acylation, phosphorylation, and glycosylation patterns.

Main Results:

  • A novel diphosphoryl hepta-acylated lipid A structure was identified in colistin-resistant A. baumannii MAC204.
  • This novel structure includes phosphoethanolamine (pEtN) and galactosamine (GalN) modifications.
  • Clinical colistin-resistant isolates exhibited the same pEtN and GalN modifications as the laboratory strain.

Conclusions:

  • The study provides complete structural characterization of lipid A in colistin-resistant A. baumannii.
  • pEtN and GalN modifications on lipid A are key determinants of colistin resistance.
  • Understanding these structural alterations is vital for developing new therapeutic strategies against MDR A. baumannii.

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