Giuseppe
Emeritus
[Source: mBio, full text: (LINK). Abstract, edited.]
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A Novel Mechanism of High-Level, Broad-Spectrum Antibiotic Resistance Caused by a Single Base Pair Change in Neisseria gonorrhoeae
Elizabeth A. Ohneck<SUP>a</SUP>, Yaramah M. Zalucki<SUP>a</SUP>, Paul J. T. Johnson<SUP>a</SUP>, Vijaya Dhulipala<SUP>a</SUP>, Daniel Golparian<SUP>b</SUP>, Magnus Unemo<SUP>b</SUP>, Ann E. Jerse<SUP>c</SUP>, and William M. Shafer<SUP>a,d</SUP>
Author Affiliations: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA<SUP>a</SUP>; Swedish Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Microbiology, ?rebro University Hospital, ?rebro, Sweden<SUP>b</SUP>; Department of Microbiology and Immunology, F. Edward H?bert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA<SUP>c</SUP>; and Laboratories of Bacterial Pathogenesis, VA Medical Center, Decatur, Georgia, USA<SUP>d</SUP>
<SUP></SUP>
Address correspondence to William M. Shafer, wshafer@emory.edu.
Editor E. Peter Greenberg, University of Washington
ABSTRACT
The MtrC-MtrD-MtrE multidrug efflux pump of Neisseria gonorrhoeae confers resistance to a diverse array of antimicrobial agents by transporting these toxic compounds out of the gonococcus. Frequently in gonococcal strains, the expression of the mtrCDE operon is differentially regulated by both a repressor, MtrR, and an activator, MtrA. The mtrR gene lies 250 bp upstream of and is transcribed divergently from the mtrCDE operon. Previous research has shown that mutations in the mtrR coding region and in the mtrR-mtrCDE intergenic region increase levels of gonococcal antibiotic resistance and in vivo fitness. Recently, a C-to-T transition mutation 120 bp upstream of the mtrC start codon, termed mtr<SUB>120</SUB>, was identified in strain MS11 and shown to be sufficient to confer high levels of antimicrobial resistance when introduced into strain FA19. Here we report that this mutation results in a consensus −10 element and that its presence generates a novel promoter for mtrCDE transcription. This newly generated promoter was found to be stronger than the wild-type promoter and does not appear to be subject to MtrR repression or MtrA activation. Although rare, the mtr<SUB>120</SUB> mutation was identified in an additional clinical isolate during sequence analysis of antibiotic-resistant strains cultured from patients with gonococcal infections. We propose that cis-acting mutations can develop in gonococci that significantly alter the regulation of the mtrCDE operon and result in increased resistance to antimicrobials.
IMPORTANCE
Gonorrhea is the second most prevalent sexually transmitted bacterial infection and a worldwide public health concern. As there is currently no vaccine against Neisseria gonorrhoeae, appropriate diagnostics and subsequent antibiotic therapy remain the primary means of infection control. However, the effectiveness of antibiotic treatment is constantly challenged by the emergence of resistant strains, mandating a thorough understanding of resistance mechanisms to aid in the development of new antimicrobial therapies and genetic methods for antimicrobial resistance testing. This study was undertaken to characterize a novel mechanism of antibiotic resistance regulation in N. gonorrhoeae. Here we show that a single base pair mutation generates a second, stronger promoter for mtrCDE transcription that acts independently of the known efflux system regulators and results in high-level antimicrobial resistance.
Footnotes
Citation Ohneck EA, et al. 2011. A novel mechanism of high-level, broad-spectrum antibiotic resistance caused by a single base pair change in Neisseria gonorrhoeae. mBio 2(5):e00187-11. doi:10.1128/mBio.00187-11.
Received 17 August 2011
Accepted 23 August 2011
Published 20 September 2011
Copyright ? 2011 Ohneck et al.
This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
-Elizabeth A. Ohneck<SUP>a</SUP>, Yaramah M. Zalucki<SUP>a</SUP>, Paul J. T. Johnson<SUP>a</SUP>, Vijaya Dhulipala<SUP>a</SUP>, Daniel Golparian<SUP>b</SUP>, Magnus Unemo<SUP>b</SUP>, Ann E. Jerse<SUP>c</SUP>, and William M. Shafer<SUP>a,d</SUP>
Author Affiliations: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA<SUP>a</SUP>; Swedish Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Microbiology, ?rebro University Hospital, ?rebro, Sweden<SUP>b</SUP>; Department of Microbiology and Immunology, F. Edward H?bert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA<SUP>c</SUP>; and Laboratories of Bacterial Pathogenesis, VA Medical Center, Decatur, Georgia, USA<SUP>d</SUP>
<SUP></SUP>
Address correspondence to William M. Shafer, wshafer@emory.edu.
Editor E. Peter Greenberg, University of Washington
ABSTRACT
The MtrC-MtrD-MtrE multidrug efflux pump of Neisseria gonorrhoeae confers resistance to a diverse array of antimicrobial agents by transporting these toxic compounds out of the gonococcus. Frequently in gonococcal strains, the expression of the mtrCDE operon is differentially regulated by both a repressor, MtrR, and an activator, MtrA. The mtrR gene lies 250 bp upstream of and is transcribed divergently from the mtrCDE operon. Previous research has shown that mutations in the mtrR coding region and in the mtrR-mtrCDE intergenic region increase levels of gonococcal antibiotic resistance and in vivo fitness. Recently, a C-to-T transition mutation 120 bp upstream of the mtrC start codon, termed mtr<SUB>120</SUB>, was identified in strain MS11 and shown to be sufficient to confer high levels of antimicrobial resistance when introduced into strain FA19. Here we report that this mutation results in a consensus −10 element and that its presence generates a novel promoter for mtrCDE transcription. This newly generated promoter was found to be stronger than the wild-type promoter and does not appear to be subject to MtrR repression or MtrA activation. Although rare, the mtr<SUB>120</SUB> mutation was identified in an additional clinical isolate during sequence analysis of antibiotic-resistant strains cultured from patients with gonococcal infections. We propose that cis-acting mutations can develop in gonococci that significantly alter the regulation of the mtrCDE operon and result in increased resistance to antimicrobials.
IMPORTANCE
Gonorrhea is the second most prevalent sexually transmitted bacterial infection and a worldwide public health concern. As there is currently no vaccine against Neisseria gonorrhoeae, appropriate diagnostics and subsequent antibiotic therapy remain the primary means of infection control. However, the effectiveness of antibiotic treatment is constantly challenged by the emergence of resistant strains, mandating a thorough understanding of resistance mechanisms to aid in the development of new antimicrobial therapies and genetic methods for antimicrobial resistance testing. This study was undertaken to characterize a novel mechanism of antibiotic resistance regulation in N. gonorrhoeae. Here we show that a single base pair mutation generates a second, stronger promoter for mtrCDE transcription that acts independently of the known efflux system regulators and results in high-level antimicrobial resistance.
Footnotes
Citation Ohneck EA, et al. 2011. A novel mechanism of high-level, broad-spectrum antibiotic resistance caused by a single base pair change in Neisseria gonorrhoeae. mBio 2(5):e00187-11. doi:10.1128/mBio.00187-11.
Received 17 August 2011
Accepted 23 August 2011
Published 20 September 2011
Copyright ? 2011 Ohneck et al.
This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
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