Related Experiment Video

Updated: Jan 3, 2026

Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
09:00

Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

Published on: May 2, 2018

12.2K

Sequence Duplication Within pmrB Gene Contribute to High-Level Colistin Resistance in Avian Pathogenic Escherichia

Jinhu Huang1, Xingyang Dai1, Lin Ge1

  • 1MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.

Microbial Drug Resistance (Larchmont, N.Y.)
|November 27, 2019
PubMed

Insights

New mutations in the pmrAB genes, specifically PmrB sequence duplications, contribute to high-level colistin resistance in Avian pathogenic Escherichia coli (APEC). These mutations also affect susceptibility to other antibiotics and bacterial cell surface properties.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Genetics

Background:

  • Mutations in pmrAB genes are a primary mechanism of colistin resistance in Escherichia coli.
  • Mechanisms driving high-level colistin resistance (HLCR) in Avian pathogenic E. coli (APEC) remain largely unknown.
  • Understanding HLCR mechanisms is crucial for effective treatment strategies against APEC infections.

Purpose of the Study:

  • To elucidate the mechanisms of high-level colistin resistance (HLCR) in colistin-susceptible APEC isolates following colistin exposure.
  • To identify novel genetic mutations associated with HLCR in APEC strains.

Main Methods:

  • Exposure of five colistin-susceptible APEC isolates to colistin to induce resistance.
  • Identification of mutations using gene sequencing, including PmrB substitutions and sequence duplications (PmrB-sd).
  • Chromosomal replacement and deletion mutagenesis to confirm the role of identified mutations.
  • Quantitative reverse transcription/polymerase chain reaction (qRT-PCR) to assess pmrAB transcript levels.
  • Determination of minimum inhibitory concentrations (MICs) for various antibiotics.
  • Zeta potential measurements to analyze cell surface charge.

Main Results:

  • Three PmrB substitutions (G19R, L167P, V88E) and two PmrB-sd mutations (68-77dup, 94-156dup) were identified in colistin-exposed APEC.
  • PmrB-sd mutations were found to contribute to, but not solely cause, HLCR in APEC.
  • PmrB-sd induction mutants showed increased pmrAB transcript levels, while reversion mutants showed reduced expression.
  • All five induction mutants displayed reduced susceptibility to florfenicol and tetracycline.
  • Specific mutants showed increased sensitivity to ceftiofur and gentamicin.
  • Induction mutants exhibited reduced negative charge on the cell surface, increased lag time, and decreased fitness.

Conclusions:

  • Novel PmrB-sd mutations contribute to high-level colistin resistance in APEC, expanding the understanding of colistin resistance mechanisms.
  • The development of colistin resistance in APEC is associated with pleiotropic effects on antibiotic susceptibility and bacterial fitness.
  • Clinical use of colistin for APEC infections requires careful consideration due to the potential for resistance development.
Keywords:
APECPmrBfitnesshigh-level colistin resistancemutationssequence duplication

More Related Videos

Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing09:44

Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing

Published on: December 23, 2022

2.8K
Antibiotic Dereplication Using the Antibiotic Resistance Platform10:49

Antibiotic Dereplication Using the Antibiotic Resistance Platform

Published on: October 17, 2019

11.5K

Related Concept Videos

Stringent Response in E. coli01:23

Stringent Response in E. coli

Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
243
Development of Antibiotic Resistance01:30

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...
1.1K
Coordination of Gene Expression Processes in Bacteria01:29

Coordination of Gene Expression Processes in Bacteria

The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...
518
Plasmids01:28

Plasmids

Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...
960
Antibiotic Selection00:57

Antibiotic Selection

Overview
59.2K
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
1.2K