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Genetic trends in a population evolving antibiotic resistance
1James H. Quillen Veterans Affairs Medical Center, Mountain Home, Tennessee 37684, USA. walkeres@etsu.edu
Evolution; International Journal of Organic Evolution
|July 28, 2001
Summary
Antibiotic resistance evolved rapidly in Moraxella catarrhalis, with high genetic diversity maintained during the transition to penicillin resistance. Horizontal gene exchange facilitated the spread of resistance determinants across diverse bacterial strains.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genetics
Background:
- Antibiotic resistance is a significant public health concern, driven by selection processes in bacterial populations.
- Moraxella catarrhalis is a common human pathogen where antibiotic resistance has emerged.
Purpose of the Study:
- To analyze the genetic changes in Moraxella catarrhalis during the transition to chromosomally encoded penicillin resistance.
- To investigate the population structure and evolutionary dynamics of antibiotic resistance acquisition.
Main Methods:
- Analysis of a comprehensive collection of Moraxella catarrhalis isolates spanning the resistance transition.
- Genomic analysis of three distinct genomic regions to assess haplotypic diversity and genetic differentiation.
- Temporal analysis of isolate data to track strain persistence, antibiotic status, and haplotype identity.
Main Results:
- High haplotypic diversity (148 haplotypes in 372 isolates) was observed throughout the resistance transition.
- No evidence of selection departures from neutrality was found, indicating stable population numbers.
- Haplotype conversions from sensitive to resistant strains, alongside evidence of clonal expansion and horizontal exchange, were documented.
Conclusions:
- Penicillin resistance determinants spread to diverse Moraxella catarrhalis strains via horizontal exchange, maintaining genetic diversity.
- The population structure, while showing evidence of clonal expansion for some haplotypes, remained largely non-clonal.
- Genetic drift at marker loci coupled with directional selection at the resistance locus explains the observed haplotype-antibiotic resistance associations.