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Detection of Plasmid-Mediated Mobile Colistin Resistance Gene (mcr-1) in Enterobacterales Isolates from a University

Mera Mohammed Galal Anan1, Eman Ahmed El-Seidi1, Marwa Salah Mostafa1

  • 1Department of Medical Microbiology and Immunology, Faculty of Medicine, Cairo University, Cairo, Egypt.

Infection and Drug Resistance
|August 19, 2021
PubMed
Abstract

Insights

A new chromogenic medium, COLR agar, shows promise for detecting colistin-resistant bacteria. This method aids in identifying multi-drug resistant Enterobacterales, crucial for managing difficult infections.

Area of Science:

  • Clinical Microbiology
  • Antimicrobial Resistance
  • Molecular Diagnostics

Background:

  • Colistin is a critical last-resort antibiotic for treating infections caused by multi-drug resistant (MDR) Enterobacterales.
  • The emergence and spread of plasmid-mediated colistin resistance genes, particularly mcr-1, pose a significant threat to public health.
  • Rapid detection of colistin resistance is essential for guiding appropriate patient treatment and infection control strategies.

Purpose of the Study:

  • To evaluate the performance of CHROMID Colistin Resistance (COLR) agar for the rapid, phenotypic detection of colistin-resistant Enterobacterales.
  • To compare COLR agar results with broth microdilution (BMD) as a reference standard.
  • To investigate the presence of mobile colistin resistance genes (mcr-1 to -5) and the insertion sequence ISAPL1 in resistant isolates using molecular methods.

Main Methods:

  • One hundred Enterobacterales isolates were tested.
  • COLR agar was used for phenotypic detection of colistin resistance.
  • Broth microdilution (BMD) served as the reference method.
  • Polymerase chain reaction (PCR) and sequencing were employed to detect and characterize mcr genes (-1 to -5) and ISAPL1.

Main Results:

  • 53% of the 100 Enterobacterales isolates exhibited colistin resistance, with higher prevalence in Klebsiella pneumoniae (75%) than Escherichia coli (44.4%).
  • COLR agar demonstrated 83.2% sensitivity and 97.9% specificity for detecting colistin resistance.
  • The mcr-1 gene was identified in 7.5% of colistin-resistant isolates (four E. coli strains); ISAPL1 was not detected in mcr-1 positive isolates.

Conclusions:

  • COLR agar is a valuable and promising phenotypic tool for the rapid identification of colistin-resistant Enterobacterales.
  • Multiplex PCR combined with sequencing is effective for the detection and characterization of mcr genes.
  • Continued surveillance for colistin resistance mechanisms in Enterobacterales is warranted.
Keywords:
CHROMID® COLR agarEnterobacteralescolistin resistancemcr genesmultiplex PCRsequencing

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