Comparative effects of overproducing the AraC-type transcriptional regulators MarA, SoxS, RarA and RamA on antimicrobial drug susceptibility in Klebsiella pneumoniae

Juan-Carlos Jiménez-Castellanos, Wan Nur Ismah Wan Ahmad Kamil, Ching Hei Phoebe Cheung, Maryann S Tobin, James Brown, Sophie G Isaac, Kate J Heesom, Thamarai Schneiders, Matthew B Avison

Research output: Contribution to journalArticle (Academic Journal)peer-review

15 Citations (Scopus)
390 Downloads (Pure)

Abstract

OBJECTIVES: In Klebsiella pneumoniae, overproduction of RamA and RarA leads to increased MICs of various antibiotics; MarA and SoxS are predicted to perform a similar function. We have compared the relative effects of overproducing these four AraC-type regulators on envelope permeability (a combination of outer membrane permeability and efflux), efflux pump and porin production, and antibiotic susceptibility in K. pneumoniae.

METHODS: Regulators were overproduced using a pBAD expression vector. Antibiotic susceptibility was measured using disc testing. Envelope permeability was estimated using a fluorescent dye accumulation assay. Porin and efflux pump production was quantified using proteomics and validated using real-time quantitative RT-PCR.

RESULTS: Envelope permeability and antibiotic disc inhibition zone diameters both reduced during overproduction of RamA and to a lesser extent RarA or SoxS, but did not change following overproduction of MarA. These effects were associated with overproduction of the efflux pumps AcrAB (for RamA and SoxS) and OqxAB (for RamA and RarA) and the outer membrane protein TolC (for all regulators). Effects on porin production were strain specific.

CONCLUSIONS: RamA is the most potent regulator of antibiotic permeability in K. pneumoniae, followed by RarA then SoxS, with MarA having very little effect. This observed relative potency correlates well with the frequency at which these regulators are reportedly overproduced in clinical isolates.

Original languageEnglish
Pages (from-to)1820-1825
Number of pages6
JournalJournal of Antimicrobial Chemotherapy
Volume71
Issue number7
Early online date29 Mar 2016
DOIs
Publication statusPublished - 7 Jul 2016

Keywords

  • antibiotics
  • transcription
  • genetic
  • cell membrane permeability
  • fluorescent dyes
  • klebsiella pneumoniae
  • membrane proteins
  • permeability
  • porin
  • reverse transcriptase polymerase chain reaction
  • antimicrobials
  • proteomics
  • antimicrobial susceptibility
  • expression vector
  • malnutrition-inflammation-cachexia syndrome

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