Host population structure and treatment frequency maintain balancing selection on drug resistance

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Updated: Feb 24, 2026

Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms
08:46

Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms

Published on: December 9, 2015

11.2K

Sarah Cobey1, Edward B Baskerville2, Caroline Colijn3

  • 1Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA cobey@uchicago.edu.

Journal of the Royal Society, Interface
|August 25, 2017
PubMed

Insights

Antimicrobial resistance in Streptococcus pneumoniae is complex. Frequent antibiotic treatment, not just use, drives resistance by impacting sensitive strains, especially in structured populations.

Area of Science:

  • Microbiology
  • Epidemiology
  • Mathematical Modeling

Background:

  • Antimicrobial drugs select for resistance, but patterns vary significantly across pathogens and populations.
  • Streptococcus pneumoniae, a common commensal, exhibits persistent coexistence of drug-sensitive and drug-resistant strains, a theoretically unlikely outcome.

Purpose of the Study:

  • To model the dynamics of competing Streptococcus pneumoniae strains.
  • To investigate how transmission dynamics and antibiotic treatment influence the stable coexistence of resistant and sensitive strains.

Main Methods:

  • Developed a mathematical model simulating competing S. pneumoniae strains.
  • Analyzed the impact of host population structure and age-assortative transmission on strain dynamics.
  • Evaluated the role of antibiotic use frequency versus rate on selective pressure.

Main Results:

  • Coexistence of resistant and sensitive strains is highly sensitive to host population structure.
  • Age-assortative transmission models with age-varying antibiotic use can explain coexistence.
  • Frequent antibiotic therapy, rather than the rate of use, disproportionately affects sensitive strains' fitness.
  • This explains why longer carriage duration correlates with higher resistance.

Conclusions:

  • Host population structure is a critical, often overlooked, factor in antimicrobial resistance dynamics.
  • Frequent antibiotic treatment is a key driver of resistance selection in commensal bacteria like S. pneumoniae.
  • Findings may apply to other pathogenic commensals, emphasizing the importance of population structure in resistance evolution.
Keywords:
antimicrobial resistanceepidemiologyinfectious disease ecology

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