Minimal functional system required for expression of erythromycin resistance by msrA in Staphylococcus aureus RN4220

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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
07:10

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues

Published on: February 19, 2019

J I Ross1, E A Eady, J H Cove

  • 1Department of Microbiology, University of Leeds, UK.

Gene
|December 12, 1996
PubMed

Insights

Chromosomal genes stpC and smpC are not required for inducible erythromycin resistance in staphylococci. Deleting the msrA leader sequence confers constitutive resistance to erythromycin and streptogramins.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Inducible erythromycin resistance in staphylococci is mediated by the plasmid-borne ABC-transporter msrA.
  • Previous studies suggested involvement of unidentified chromosomally encoded transmembrane domains.
  • Candidate genes stpC and smpC, similar to sequences near msrA, were investigated.

Purpose of the Study:

  • To investigate the requirement of S. aureus sequences stpC and smpC for erythromycin resistance.
  • To determine the minimal functional unit of MsrA required for resistance.
  • To clarify the relationship between erythromycin and streptogramin resistance.

Main Methods:

  • Allelic replacement using electroporation of S. aureus RN4220 with a suicide vector to create delta(stpC-smpC) mutations.
  • Deletion of the control region within the leader sequence of msrA.
  • Construction and testing of deletion constructs of MsrA's ABC regions.

Main Results:

  • Deletion of stpC and smpC did not affect the erythromycin resistance phenotype.
  • Deletion of the msrA leader sequence resulted in constitutive resistance to erythromycin and type B streptogramins.
  • Deletion constructs of MsrA's ABC regions did not confer erythromycin resistance.

Conclusions:

  • The stpC and smpC genes are not required for inducible erythromycin resistance in staphylococci.
  • Erythromycin resistance mediated by msrA does not require additional chromosomally encoded factors.
  • Constitutive resistance and streptogramin resistance are separable from inducible erythromycin resistance and do not require the presence of erythromycin.

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