Clonal spread of IMP-1-producing Pseudomonas aeruginosa in two hospitals in Singapore

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Pseudomonas aeruginosa is an opportunistic pathogen frequently associated with healthcare-associated infections.
• Carbapenem resistance in P. aeruginosa is a growing global health concern, limiting treatment options.
• The bla genes, encoding carbapenemases, are a primary mechanism of carbapenem resistance.

Purpose of the Study:

• To investigate the genetic relatedness and carbapenemase gene content of carbapenem-resistant Pseudomonas aeruginosa isolates.
• To identify the specific carbapenemase genes and their genetic variations present in the studied isolates.

Main Methods:

• Thirty-six isolates of carbapenem-resistant Pseudomonas aeruginosa were subjected to genotypic analysis.
• Pulsed-field gel electrophoresis (PFGE) was employed to assess clonal relationships among the isolates.
• Molecular methods were used to detect and characterize carbapenemase genes, specifically bla genes.

Main Results:

• Pulsed-field gel electrophoresis identified two distinct clonal groups among the 36 isolates.
• One major clone harbored the bla(IMP-1) gene, identical to previously reported strains.
• A second clone carried a variant of the bla(IMP-1) gene featuring four silent mutations. A unique isolate contained the bla(IMP-7) gene.

Conclusions:

• The study highlights the clonal dissemination of carbapenem-resistant Pseudomonas aeruginosa.
• The presence of both identical and variant bla(IMP-1) genes suggests ongoing genetic evolution and spread.
• The identification of bla(IMP-7) in a unique isolate underscores the diversity of carbapenemase mechanisms in P. aeruginosa.