1. Academic Validation
  2. cis- and trans-Acting Factors Influence Expression of the norM-Encoded Efflux Pump of Neisseria gonorrhoeae and Levels of Gonococcal Susceptibility to Substrate Antimicrobials

cis- and trans-Acting Factors Influence Expression of the norM-Encoded Efflux Pump of Neisseria gonorrhoeae and Levels of Gonococcal Susceptibility to Substrate Antimicrobials

  • Antimicrob Agents Chemother. 2018 Jul 27;62(8):e00821-18. doi: 10.1128/AAC.00821-18.
Corinne E Rouquette-Loughlin 1 Vijaya Dhulipala 1 Jennifer L Reimche 1 Erica Raterman 2 Afrin A Begum 2 Ann E Jerse 2 William M Shafer 3 4 5
Affiliations

Affiliations

  • 1 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA.
  • 2 Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University, Bethesda, Maryland, USA.
  • 3 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA wshafer@emory.edu.
  • 4 The Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA.
  • 5 Laboratories of Bacterial Pathogenesis, VA Medical Center, Decatur, Georgia, USA.
Abstract

The gonococcal NorM efflux pump exports substrates with a cationic moiety, including quaternary ammonium compounds such as berberine (BE) and ethidium bromide (EB) as well as Antibiotics such as ciprofloxacin and solithromycin. The norM gene is part of a four-gene operon that is transcribed from a promoter containing a polynucleotide tract of 6 or 7 thymidines (T's) between the -10 and -35 hexamers; the majority of gonococcal strains analyzed in this study contained a T-6 sequence. Primer extension analysis showed that regardless of the length of the poly(T) tract, the same transcriptional start site (TSS) was used for expression of norM Interestingly, the T-6 tract correlated with a higher level of both norM expression and gonococcal resistance to NorM substrates BE and EB. Analysis of expression of genes downstream of norM showed that the product of the tetR-like gene has the capacity to activate expression of norM as well as murB, which encodes an acetylenolpyroylglucosamine reductase predicted to be involved in the early steps of peptidoglycan synthesis. Moreover, loss of the TetR-like transcriptional regulator modestly increased gonococcal susceptibility to NorM substrates EB and BE. We conclude that both cis- and trans-acting regulatory systems can regulate expression of the norM operon and influence levels of gonococcal susceptibility to antimicrobials exported by NorM.

Keywords

NorM; efflux pumps; gonorrhea; resistance.

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