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Proc Natl Acad Sci U S A. 2015 Mar 17;112(11):3511-6. doi: 10.1073/pnas.1419939112. Epub 2015 Mar 3.

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

Author information

1
Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, United Kingdom;
2
School of Engineering and Science, Jacobs University Bremen, 28759 Bremen, Germany; and.
3
Department of Physics, University of Cagliari, 09042 Monserrato, Italy.
4
Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, United Kingdom; l.j.v.piddock@bham.ac.uk.

Abstract

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.

KEYWORDS:

AcrB; antimicrobial resistance; efflux; whole genome sequencing

PMID:
25737552
PMCID:
PMC4371985
DOI:
10.1073/pnas.1419939112
[Indexed for MEDLINE]
Free PMC Article

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