Evaluating the level of nitroreductase activity in clinical Klebsiella pneumoniae isolates to support strategies for nitro drug and prodrug development

Matthew Wand, Holly V. Taylor, Jennifer L. Auer, Lucy Bock, Charlotte K. Hind, Shirin Jamshidi, Khondaker Miraz Rahman, J. Mark Sutton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

To understand the potential utility of novel nitroreductase (NR)-activated prodrugs, NR enzyme activity was assessed in clinical Klebsiella pneumoniae isolates using a NR-activated fluorescent probe. NR activity was constant throughout the bacterial growth cycle, but individual K. pneumoniae isolates exhibited a wide range of NR activity levels. The genes of major NR enzymes (nfsA and nfnB) showed a number of sequence variants. Aside from a C-terminal extension of NfnB, which may be responsible for lower NR activity in specific isolates, the genetic differences did not explain the variation in activity. Analysis of important clinical strains (ST11, ST258, ST14 and ST101) showed significant variation in NR activity between isolates within the same sequence type despite conservation of nfsA/nfnB sequences. Addition of methyl viologen (MV), a known activator of soxRS, caused a significant increase in NR activity for all strains, with proportionally larger increases in activity seen for strains with low uninduced NR levels. Real-time PCR on selected strains following exposure to MV showed upregulation of soxS (15–32-fold) and nfsA (5–22-fold) in all strains tested. Expression of nfnB was upregulated 2–5-fold in 4/6 strains tested. High levels of NR activity in the absence of MV activation correlated with nitrofurantoin susceptibility. These data provide evidence that NR gene mutations and regulatory pathways influence NR activity in K. pneumoniae isolates and this is likely to impact treatment efficacy with novel nitro-containing drugs or prodrugs.

Original languageEnglish
Pages (from-to)538-546
Number of pages9
JournalInternational Journal of Antimicrobial Agents
Volume54
Issue number5
DOIs
Publication statusPublished - Nov 2019

Bibliographical note

Funding Information:
Funding: This work was supported by Public Health England [Grant-in-Aid project 109506]. Competing interests: None declared. Ethical approval: Not required.

Funding Information:
The authors acknowledge the assistance of Dr Katie Hopkins and Dr Daniele Meunier [Antimicrobial Resistance and Healthcare Associated Infections (AMR-HAI) Reference Unit, National Infection Service, Public Health England (PHE), London, UK] for the provision and phenotypic characterisation of strains used in this study. The opinions expressed are those of the authors and are not necessarily the opinions of PHE. Funding: This work was supported by Public Health England [Grant-in-Aid project 109506]. Competing interests: None declared. Ethical approval: Not required.

Publisher Copyright:
© 2019

Keywords

  • Klebsiella pneumoniae
  • Methyl viologen
  • Nitroreductase
  • Prodrug
  • nfsA
  • soxRS

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