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Measuring Microbial Mutation Rates with the Fluctuation Assay
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Fluoroquinolone resistance in Haemophilus influenzae is associated with hypermutability

María Pérez-Vázquez1, Federico Román, Silvia García-Cobos

  • 1Antibiotic Laboratory, Bacteriology Service, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain.

Antimicrobial Agents and Chemotherapy
|February 7, 2007
PubMed

Insights

A significant proportion of ciprofloxacin-nonsusceptible Haemophilus influenzae respiratory isolates are hypermutable. These hypermutable strains are crucial for developing multi-step resistance mechanisms to fluoroquinolone antibiotics.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Genetics

Background:

  • Ciprofloxacin (CIP) resistance in Haemophilus influenzae is a growing concern.
  • Hypermutability is a known factor contributing to antimicrobial resistance.
  • Understanding resistance mechanisms is vital for effective treatment strategies.

Purpose of the Study:

  • To investigate the prevalence of hypermutability in ciprofloxacin-nonsusceptible Haemophilus influenzae.
  • To explore the resistance mechanisms developed by these nonsusceptible strains.

Main Methods:

  • Comparative analysis of ciprofloxacin-susceptible and -nonsusceptible Haemophilus influenzae isolates.
  • Identification and characterization of resistance mechanisms in developed mutants.

Main Results:

  • Forty-three percent of ciprofloxacin-nonsusceptible isolates were hypermutable, significantly higher than the 8.5% in susceptible isolates (P=0.002).
  • Ciprofloxacin-nonsusceptible mutants were exclusively derived from hypermutable strains.
  • A three-step resistance development process was observed: target modification, porin loss, and increased efflux.

Conclusions:

  • Hypermutability is strongly associated with ciprofloxacin nonsusceptibility in Haemophilus influenzae.
  • Hypermutable strains facilitate the stepwise acquisition of multiple resistance mechanisms.
  • These findings highlight the importance of monitoring hypermutability in clinical settings to predict and manage fluoroquinolone resistance.

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