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Related Concept Videos

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Inhibitors of Bacterial DNA Synthesis

Bacterial pathogens depend on precise and efficient DNA replication to sustain infection. Two type II topoisomerases—DNA gyrase and topoisomerase IV—are critical to this process, as they resolve DNA supercoiling and unlink chromosomes during replication. Fluoroquinolones, synthetic derivatives of quinolones, exploit this mechanism by stabilizing the transient DNA–enzyme cleavage complex, preventing strand religation, and causing lethal double-strand breaks. These antibiotics are selectively...
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Cholera is an acute gastrointestinal disease caused by the Gram-negative bacterium Vibrio cholerae. It is transmitted primarily via the fecal-oral route through the ingestion of contaminated water or food.Vibrio cholerae is a motile, Gram-negative bacterium of the family Vibrionaceae, primarily associated with waterborne outbreaks in areas with inadequate sanitation. Although over 200 serogroups of V. cholerae exist, only O1 and O139 are responsible for epidemic cholera. The O1 serogroup,...
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Related Experiment Video

Updated: Jul 4, 2026

Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing
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Published on: December 23, 2022

Quinolone-resistant Escherichia coli.

Carmen Antonia Sanches Ito1, Ana Cristina Gales, Maria Cristina B Tognim

  • 1State University of Ponta Grossa, Ponta Grossa, PR, Brazil.

The Brazilian Journal of Infectious Diseases : an Official Publication of the Brazilian Society of Infectious Diseases
|June 17, 2008
PubMed
Summary

Nalidixic acid (NAL) effectively predicts fluoroquinolone susceptibility in Escherichia coli, with 100% sensitivity. This finding supports using NAL as a marker for antimicrobial resistance surveillance.

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Published on: October 29, 2014

Area of Science:

  • Clinical Microbiology
  • Antimicrobial Resistance
  • Molecular Biology

Background:

  • Quinolone antibiotics are crucial for treating urinary tract infections.
  • Rising antimicrobial resistance necessitates effective surveillance methods.
  • Understanding resistance mechanisms guides appropriate antibiotic use.

Purpose of the Study:

  • To evaluate nalidixic acid (NAL) as a marker for fluoroquinolone susceptibility in *Escherichia coli*.
  • To determine the prevalence of quinolone resistance in clinical isolates.
  • To investigate the genetic basis of quinolone resistance.

Main Methods:

  • Disk diffusion (DD) and agar dilution (AD) methods were used to test *E. coli* (n=385) against NAL, norfloxacin (NOR), ciprofloxacin (CIP), and gatifloxacin (GAT).
  • Susceptibility testing was correlated with mutations in the quinolone resistance-determining region (QRDR) of *gyrA* and *parC* genes via sequencing.
  • NAL susceptibility by DD was assessed for its predictive value for NOR, CIP, and GAT susceptibility by AD.

Main Results:

  • An overall quinolone resistance rate of 13.8% was observed.
  • NAL demonstrated 100% sensitivity and 95% specificity in predicting fluoroquinolone susceptibility.
  • Mutations in *gyrA* and *parC* were identified in resistant isolates, correlating with resistance patterns.

Conclusions:

  • Nalidixic acid can serve as a reliable marker for fluoroquinolone susceptibility in routine microbiology labs.
  • The observed 13.8% quinolone resistance rate is concerning and higher than in some developed countries.
  • Continuous monitoring of antimicrobial resistance is essential to combat increasing resistance trends.