AcrB drug-binding pocket substitution confers clinically relevant resistance and altered substrate specificity

Jessica M. A. Blair, Vassiliy N. Bavro, Vito Ricci, Niraj Modi, Pierpaolo Cacciotto, Ulrich Kleinekathӧfer, Paolo Ruggerone, Attilio V. Vargiu, Alison J. Baylay, Helen E. Smith, Yvonne Brandon, David Galloway, Laura J. V. Piddock

Research output: Contribution to journalArticlepeer-review

88 Citations (Scopus)


The incidence of multidrug-resistant bacterial infections is increasing globally and the need to understand the underlying mechanisms is paramount to discover new therapeutics. The efflux pumps of Gram-negative bacteria have a broad substrate range and transport antibiotics out of the bacterium, conferring intrinsic multidrug resistance (MDR). The genomes of pre- and posttherapy MDR clinical isolates of Salmonella Typhimurium from a patient that failed antibacterial therapy and died were sequenced. In the posttherapy isolate we identified a novel G288D substitution in AcrB, the resistance-nodulation division transporter in the AcrAB-TolC tripartite MDR efflux pump system. Computational structural analysis suggested that G288D in AcrB heavily affects the structure, dynamics, and hydration properties of the distal binding pocket altering specificity for antibacterial drugs. Consistent with this hypothesis, recreation of the mutation in standard Escherichia coli and Salmonella strains showed that G288D AcrB altered substrate specificity, conferring decreased susceptibility to the fluoroquinolone antibiotic ciprofloxacin by increased efflux. At the same time, the substitution increased susceptibility to other drugs by decreased efflux. Information about drug transport is vital for the discovery of new antibacterials; the finding that one amino acid change can cause resistance to some drugs, while conferring increased susceptibility to others, could provide a basis for new drug development and treatment strategies.
Original languageEnglish
Pages (from-to)3511-3516
JournalNational Academy of Sciences. Proceedings
Issue number11
Early online date3 Mar 2015
Publication statusPublished - 17 Mar 2015


  • AcrB
  • antimicrobial resistance
  • efflux
  • whole genome sequencing


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