Related Experiment Video

Updated: Feb 22, 2026

Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method
12:03

Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method

Published on: April 18, 2019

27.8K

Polymyxin susceptibility testing, interpretative breakpoints and resistance mechanisms: An update

Yamuna Devi Bakthavatchalam1, Agila Kumari Pragasam1, Indranil Biswas2

  • 1Department of Clinical Microbiology, Christian Medical College, Vellore 632004, Tamil Nadu, India.

Journal of Global Antimicrobial Resistance
|October 1, 2017
PubMed

Insights

Accurate polymyxin susceptibility testing is crucial for treating multidrug-resistant infections. This review discusses challenges and methods for testing colistin and polymyxin B, including new resistance mechanisms.

Area of Science:

  • Clinical microbiology
  • Infectious diseases
  • Antimicrobial resistance

Background:

  • Multidrug-resistant (MDR) nosocomial pathogens pose a significant threat.
  • Polymyxins are last-resort antibiotics for MDR Gram-negative bacterial infections.
  • Routine polymyxin susceptibility testing is essential due to increased usage.

Purpose of the Study:

  • To review current polymyxin susceptibility testing methods.
  • To discuss challenges impacting test performance.
  • To describe emerging resistance mechanisms.

Main Methods:

  • Literature review of available susceptibility testing methods.
  • Discussion of factors affecting test accuracy (e.g., drug composition, diffusion, adsorption, synergy).
  • Overview of identified chromosomal and plasmid-mediated resistance mechanisms.

Main Results:

  • Polymyxin susceptibility testing is challenging due to drug properties and interactions.
  • Factors like multicomponent composition, poor agar diffusion, and polysorbate 80 synergy affect results.
  • New resistance mechanisms include LPS modification (L-Ara4-N, pEtN) and plasmid-borne mcr genes.

Conclusions:

  • Standardized and reliable polymyxin susceptibility testing methods are needed.
  • Understanding resistance mechanisms is vital for effective treatment strategies.
  • Continued research is necessary to combat emerging MDR pathogens.
Keywords:
ColistinMultidrug-resistantPolymyxin resistancemcr-1

More Related Videos

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes08:58

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes

Published on: March 3, 2023

8.1K
Antibiotic Dereplication Using the Antibiotic Resistance Platform10:49

Antibiotic Dereplication Using the Antibiotic Resistance Platform

Published on: October 17, 2019

11.7K

Related Concept Videos

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...
1.6K
Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism01:21

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...
768
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu01:29

Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu

Genetic variations significantly influence drug response through pharmacokinetics, receptor interactions, and biologic milieu modifications. Pharmacokinetic alterations impact drug metabolism and clearance, affecting efficacy and toxicity. Variants in drug-metabolizing enzymes, such as CYP2C9 and CYP2C19, alter drug activation and elimination. For example, CYP2C9 loss-of-function variants require lower warfarin doses to prevent excessive bleeding, while CYP2C19 variants reduce clopidogrel...
24
Combined Effects of Drugs: Synergism01:27

Combined Effects of Drugs: Synergism

Synergism is a useful mechanism where combining two or more drugs is more effective than each constituent used alone. Such combinations are also called supra-additive interactions. The drugs collectively enhance the final therapeutic effect by acting on different targets. Another advantage is that the low dose of each constituent drug is sufficient to achieve the desired effect. This helps reduce the duration of therapy and lower the adverse effects of these drugs.
Such synergistic combinations...
7.0K
Pharmacodynamic Models: Overview01:27

Pharmacodynamic Models: Overview

Pharmacodynamic (PD) responses describe the interaction between a drug and its biological target, culminating in a physiological effect. These responses can be classified into different types: continuous variables, such as blood glucose levels; categorical outcomes, like survival rates; and time-to-event metrics, such as disease progression. Understanding and modeling PD responses are critical for optimizing drug efficacy and safety.PD models describe the relationship between drug concentration...
22
Pharmacogenetics of Drug Metabolism: Overview01:27

Pharmacogenetics of Drug Metabolism: Overview

Genetic polymorphism in drug metabolism is crucial to the inter-individual variability observed in drug responses. Drug metabolism primarily involves the chemical modification of drugs and other xenobiotics to enhance their elimination by increasing their polarity. Two main classes of enzymes mediate this biotransformation process: Phase I enzymes, primarily cytochrome P450s, catalyze oxidation and reduction reactions, while other enzymes, such as esterases, mediate hydrolysis, and Phase II...
31