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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
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Published on: March 3, 2023

Fluoroquinolone resistance in Streptococcus dysgalactiae subsp. equisimilis and evidence for a shared global gene

M D Pinho1, J Melo-Cristino, M Ramirez

  • 1Instituto de Microbiologia, Faculdade de Medicina Lisboa, Universidade de Lisboa, Lisbon, Portugal.

Antimicrobial Agents and Chemotherapy
|February 11, 2010
PubMed

Insights

Quinolone resistance in Streptococcus dysgalactiae is linked to genetic mutations. Recombination between Streptococcus dysgalactiae and Streptococcus pyogenes may share resistance genes, impacting human infections.

Area of Science:

  • Microbiology
  • Genetics
  • Antimicrobial Resistance

Background:

  • Quinolone resistance is a growing concern in Streptococcus pyogenes infections.
  • Genetic recombination between Streptococcus dysgalactiae and Streptococcus pyogenes is suspected as a key mechanism for resistance.
  • Streptococcus dysgalactiae subspecies equisimilis causes human infections.

Purpose of the Study:

  • To investigate levofloxacin resistance in Streptococcus dysgalactiae subsp. equisimilis.
  • To identify genetic mechanisms underlying quinolone resistance in this species.
  • To explore potential gene sharing between S. dysgalactiae and S. pyogenes.

Main Methods:

  • Characterization of 314 S. dysgalactiae subsp. equisimilis isolates.
  • Pulsed-field gel electrophoresis for genetic profiling.
  • Sequencing of gyrA and parC genes to identify mutations.

Main Results:

  • 12% of isolates exhibited levofloxacin resistance, linked to diverse emm types and lineages.
  • No evidence for efflux pump involvement in resistance.
  • High diversity in parC alleles (19) compared to gyrA alleles (5).
  • Single gyrA or parC mutations conferred intermediate resistance; dual mutations led to higher resistance.
  • Recombination with S. pyogenes DNA observed in some parC alleles, but not solely linked to resistance.

Conclusions:

  • A shared reservoir of quinolone resistance genes likely exists between S. dysgalactiae subsp. equisimilis and S. pyogenes.
  • No evidence of recombination with S. dysgalactiae subsp. dysgalactiae was found.
  • Genetic mutations in gyrA and parC are critical for quinolone resistance development.

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