# Examining fluoroquinolone-induced DNA damage in persisters and its contributions to antibiotic resistance.

> **NIH NIH R01** · PRINCETON UNIVERSITY · 2020 · $399,792

## Abstract

Summary
 Infections that contain biofilms are exceptionally difficult to treat. These infections often respond to antibiotic
therapy but quickly relapse, resulting in chronic and recurrent infections. The recalcitrance of biofilm infections
is thought to arise from the presence of bacterial persisters. Persisters are antibiotic-tolerant cells that are
genetically identical to the overall population that succumbs to antibiotics, but occupy a favorable phenotypic
niche at the time of treatment. In general, these survivors are thought to be in a state of dormancy, where the
activities of antibiotic primary targets are reduced and the extent of antibiotic-induced damage is severely
limited. The current model of a biofilm infection cycle includes clearance of normal cells by antibiotics and
immunity, both within the film and shed from it, and clearance of persisters that are shed from the film by
immunity. Immune cells are hindered from accessing persisters within the biofilm, and when the antibiotic
levels drop, persisters proceed to repopulate the film, causing a relapse infection. With every relapse, the
chance for an antibiotic-resistant mutation to occur increases, and since persisters are thought to suffer little to
no injury from antibiotic treatment, the rate at which resistant mutants should arise from persister-spawned
cultures has been assumed to be the same as that of normal bacterial populations. Recently, we discovered
that persisters to fluoroquinolones (FQ) in growth-inhibited populations experience FQ-induced DNA damage
that is equivalent to damage in bacteria that die from treatment. These unexpected results suggested that
those persisters might be mutagenized by FQ and that populations grown up from persisters, such as those of
relapse infections, would be genetically diverse and produce antibiotic-resistant mutants at high rates, which
we found to be true. These data suggest that there is a highway between persistence and antibiotic resistance
whose entrance ramp is treatment with a commonly prescribed class of antibiotics, FQs. We hypothesize that
increased understanding of FQ damage in persisters and how they survive that damage will illuminate
strategies to reduce relapse infections and hinder antibiotic resistance development. To test our hypothesis,
we will tailor a method that quantifies DNA double-strand breaks (DSBs) at the genome-scale to FQ-induced
DSBs and employ it to study strains with different persister levels; use time-lapse microscopy to interrogate the
roles of the SOS response, DNA repair, elongation, and septation to the recovery of persisters following FQ
treatment; and use genetic mutants, lineage tracking, and whole-genome sequencing to determine whether
FQ-induced mutagenesis contributes to heightened antibiotic resistance in populations derived from FQ
persisters. Collectively, these experiments and the statistical methods we will use to analyze the resulting data
will provide mechanistic knowledge of FQ pe...

## Key facts

- **NIH application ID:** 9987499
- **Project number:** 5R01AI130293-04
- **Recipient organization:** PRINCETON UNIVERSITY
- **Principal Investigator:** Mark P Brynildsen
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $399,792
- **Award type:** 5
- **Project period:** 2017-08-01 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9987499

## Citation

> US National Institutes of Health, RePORTER application 9987499, Examining fluoroquinolone-induced DNA damage in persisters and its contributions to antibiotic resistance. (5R01AI130293-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9987499. Licensed CC0.

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