Neustria gonorrhoeae is a strict human pathogen that causes greater than sixty million cases worldwide of the sexually transmitted disease gonorrhea each year. Without an effective vaccine, antibiotic therapy remains the principle mechanism to reduce or block the transmission of the gonococcus in the community. Unfortunately, because of the development of mutations or the acquisition of resistance determinants, the gonococcus has developed resistance to relatively inexpensive antibiotics;such resistance now requires the use of more expensive antibiotics that are not always available in poor countries. Multidrug efflux pumps possessed by gonococci have an important role in the ability of gonococci to resist antibiotics and antimicrobials of the innate host defensive system. In particular, our work has shown that the MtrC-MtrD-MtrE efflux pump participates in gonococcal resistance to penicillin and macrolides. This efflux pump also recognizes host antimicrobials, such as antimicrobial peptides and progesterone. We have shown that the pump is required for gonococci to cause a sustained infection in experimentally-infected female mice and the degree of in vivo fitness is linked to transcriptional regulators that control mtrCDE gene expression. The importance of DNA- binding proteins in regulating gonococcal resistance to antimicrobials is the topic of this competitive renewal application.
In Specific Aim 1 we will define the transcriptional control processes that modulate expression of the mtrR gene, which encodes a repressor of the mtrCDE efflux pump operand and can control the expression of numerous genes outside of the mar locus. We will assess the importance of such regulation in the ability of gonococci to resist antimicrobials and during infection in experimentally-infected mice.
In Specific Aim 2 we will define the use, regulation and biologic importance of distinct promoters for transcription of the mtrCDE operand.
In Specific Aim 3 we will define the mechanism which the products of genes controlled by MtrR and other regulatory proteins impact levels of gonococcal susceptibility to antibiotics and host-derived antimicrobials. The results from the proposed work will advance our knowledge regarding how gonococci and other human bacterial pathogens use drug efflux pumps and transcriptional regulatory systems to resist both classical antibiotics as well as mediators of innate immunity.

Public Health Relevance

The goal of this project is to understand how Neustria gonorrhoeae uses drug efflux pumps and transcriptional regulators that control levels of efflux pumps and other structures to resist antibiotics or antimicrobials used by the human host during infection. The information gained will help in the development of new antimicrobials to treat or prevent gonorrhea, which remains a worldwide public health problem.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Method to Extend Research in Time (MERIT) Award (R37)
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Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
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Hiltke, Thomas J
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Emory University
Schools of Medicine
United States
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Shafer, William M (2018) Mosaic Drug Efflux Gene Sequences from Commensal Neisseria Can Lead to Low-Level Azithromycin Resistance Expressed by Neisseria gonorrhoeae Clinical Isolates. MBio 9:
Kahler, Charlene M; Nawrocki, K L; Anandan, A et al. (2018) Structure-Function Relationships of the Neisserial EptA Enzyme Responsible for Phosphoethanolamine Decoration of Lipid A: Rationale for Drug Targeting. Front Microbiol 9:1922
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Rouquette-Loughlin, Corinne E; Reimche, Jennifer L; Balthazar, Jacqueline T et al. (2018) Mechanistic Basis for Decreased Antimicrobial Susceptibility in a Clinical Isolate of Neisseria gonorrhoeae Possessing a Mosaic-Like mtr Efflux Pump Locus. MBio 9:
Rouquette-Loughlin, Corinne E; Zalucki, Yaramah M; Dhulipala, Vijaya L et al. (2017) Control of gdhR Expression in Neisseria gonorrhoeae via Autoregulation and a Master Repressor (MtrR) of a Drug Efflux Pump Operon. MBio 8:
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Vidyaprakash, Eshaw; Abrams, A Jeanine; Shafer, William M et al. (2017) Whole-Genome Sequencing of a Large Panel of Contemporary Neisseria gonorrhoeae Clinical Isolates Indicates that a Wild-Type mtrA Gene Is Common: Implications for Inducible Antimicrobial Resistance. Antimicrob Agents Chemother 61:
Shafer, William M (2016) Does the Cervicovaginal Microbiome Facilitate Transmission of Neisseria gonorrhoeae From Women to Men? Implications for Understanding Transmission of Gonorrhea and Advancing Vaccine Development. J Infect Dis 214:1615-1617
Kandler, Justin L; Acevedo, Rosuany VĂ©lez; Dickinson, Mary Kathryne et al. (2016) The genes that encode the gonococcal transferrin binding proteins, TbpB and TbpA, are differentially regulated by MisR under iron-replete and iron-depleted conditions. Mol Microbiol 102:137-51
Unemo, Magnus; Del Rio, Carlos; Shafer, William M (2016) Antimicrobial Resistance Expressed by Neisseria gonorrhoeae: A Major Global Public Health Problem in the 21st Century. Microbiol Spectr 4:

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