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Identification of Plasmid-Mediated Colistin Resistance in Multidrug-Resistant Gram-Negative Rods Isolated From

Yusra Wahab1, Humera Javed2, Shah Jahan3

  • 1Pathology and Laboratory Medicine, Faisalabad Medical University, Faisalabad, PAK.

Cureus
|July 23, 2026
PubMed
Abstract

Insights

Colistin resistance in Gram-negative bacteria is a growing concern, especially for immunocompromised patients. This study found 6% colistin resistance, with all resistant isolates carrying the mcr-1 gene, highlighting a significant threat.

Area of Science:

  • Clinical microbiology
  • Infectious diseases
  • Antimicrobial resistance

Background:

  • Antimicrobial resistance (AMR) is a major threat to immunocompromised patients, particularly multidrug-resistant (MDR) Gram-negative bacteria.
  • Colistin is a last-resort antibiotic, but the emergence of mobilized colistin resistance (mcr) genes threatens its efficacy.

Purpose of the Study:

  • To evaluate the prevalence of phenotypic colistin resistance in clinical isolates from immunocompromised patients.
  • To determine the presence of mcr genes (mcr-1 to mcr-5) in colistin-resistant isolates.

Main Methods:

  • A descriptive cross-sectional study of 100 MDR Gram-negative rods from immunocompromised patients.
  • Colistin susceptibility testing using the colistin broth disk elution (CBDE) method.
  • Polymerase chain reaction (PCR) to screen for mcr-1 to mcr-5 genes.

Main Results:

  • A 6% prevalence of phenotypic colistin resistance was observed.
  • All colistin-resistant isolates (6/6) harbored the mcr-1 gene; no other mcr genes were detected.
  • Highest resistance rates were found in Klebsiella pneumoniae (16%) and Acinetobacter baumannii (7.7%).

Conclusions:

  • The presence of mcr-1 in all resistant isolates suggests plasmid-mediated transmission, posing a significant risk to immunocompromised populations.
  • The CBDE method is a reliable diagnostic tool for colistin resistance, even in resource-limited settings.
Keywords:
colistin broth disc elution (cbde)colistin resistancegram negative rodsimmunocompromised patientsmcr-1 gene

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