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Updated: Jul 17, 2026

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
08:58

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes

Published on: March 3, 2023

Hydration and hydrolysis define antibiotic resistance conferred by macrolide esterases

Emma T R Kelly1,2,3, Iryna Myziuk4, Mark Z Hemmings1,2,3

  • 1Department of Biochemistry, McGill University, Montréal, QC H3A 1A3, Canada.

Proceedings of the National Academy of Sciences of the United States of America
|July 15, 2026
PubMed

Insights

Bacteria are developing resistance to macrolide antibiotics through enzymes called macrolide esterases. This study reveals how Est-type esterases bind to macrolides, offering insights for developing new antibiotics.

Area of Science:

  • Microbiology
  • Biochemistry
  • Structural Biology

Background:

  • Macrolide antibiotics are crucial in human and veterinary medicine but face widespread bacterial resistance.
  • Enzyme-mediated inactivation, particularly by macrolide esterases, is a significant mechanism of macrolide resistance.
  • Est-type macrolide esterases, belonging to the α/β-hydrolase superfamily, represent a recently identified class of resistance enzymes.

Purpose of the Study:

  • To conduct detailed structure-function studies on four diverse Est-type macrolide esterases.
  • To elucidate the structural basis of macrolide-enzyme interactions and substrate specificity.
  • To provide insights for the development of next-generation antibiotics.

Main Methods:

  • X-ray crystallography to determine enzyme structures, including complexes with macrolides.
  • Resistance profiling and substrate specificity assays.
  • Mutational and kinetic studies to analyze enzyme-macrolide interactions.

Main Results:

  • Detailed structures of four Est-type esterases (EstTSf, EstTSt, EstTBc, EstXEc) were determined.
  • Structures of EstTBc and EstXEc in complex with tylosin and tylvalosin, post-hydrolysis, were elucidated.
  • Analysis revealed that promiscuous binding and imprecise positioning, facilitated by a water-cage, govern substrate specificity.

Conclusions:

  • Est-type macrolide esterases exhibit substrate specificity influenced by flexible binding mechanisms.
  • Understanding these interactions is key to overcoming macrolide resistance.
  • The findings offer a foundation for designing novel antibiotics that circumvent existing resistance strategies.
Keywords:
X-ray crystallographyantimicrobial resistanceesterasehydrolasesmacrolides

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