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

Area of Science:

• Clinical microbiology
• Infectious diseases
• Antimicrobial resistance research

Background:

• Antimicrobial resistance (AMR) is a major threat to immunocompromised patients, especially 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.
• To detect the presence of mcr-1 to mcr-5 genes in clinical isolates from immunocompromised patients.

Main Methods:

• A 12-month 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) for mcr-1 to mcr-5 gene detection.

Main Results:

• A 6% colistin resistance rate was observed, predominantly in Klebsiella pneumoniae and Acinetobacter baumannii.
• All colistin-resistant isolates (6/6) harbored the mcr-1 gene; no other mcr genes were detected.
• High resistance rates were also noted for cephalosporins and carbapenems.

Conclusions:

• The 6% colistin resistance, linked to mcr-1, poses a significant risk to immunocompromised patients due to potential plasmid-mediated spread.
• The CBDE method is a reliable diagnostic tool for colistin resistance, especially in resource-limited settings.