Chromosomally Encoded mcr-5 in Colistin-Nonsusceptible Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Genomics
• Antimicrobial Resistance

Background:

• Pseudomonas aeruginosa is an opportunistic pathogen known for its intrinsic resistance to antibiotics.
• Colistin is a last-resort antibiotic used to treat infections caused by multidrug-resistant Gram-negative bacteria.
• The emergence of colistin resistance mechanisms is a significant global health concern.

Purpose of the Study:

• To investigate the genetic basis of colistin nonsusceptibility in a historical Pseudomonas aeruginosa clinical isolate.
• To identify novel resistance determinants in P. aeruginosa.

Main Methods:

• Whole-genome sequencing (WGS) was performed on a historical P. aeruginosa clinical isolate (MRSN 12280).
• Broth microdilution was used to determine colistin susceptibility.
• Bioinformatic analysis was conducted to identify resistance genes and mutations.

Main Results:

• A chromosomal copy of the mcr-5 gene, located within a Tn3-like transposon, was identified in P. aeruginosa MRSN 12280.
• The isolate exhibited nonsusceptibility to colistin.
• No previously known mutations conferring colistin resistance were found in the isolate's genome.

Conclusions:

• This study reports the first instance of the mcr-5 gene in a colistin-nonsusceptible P. aeruginosa isolate.
• The presence of mcr-5 in P. aeruginosa represents a novel mechanism of colistin resistance, potentially complicating treatment strategies.
• Further research is needed to understand the prevalence and clinical implications of mcr-5 in P. aeruginosa.