Genetic environments of the transferable plasmid-mediated blaCTX-M-3 gene in Serratia marcescens isolates

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• The blaCTX-M-3 gene confers resistance to cefotaxime, a critical antibiotic.
• Serratia marcescens is an opportunistic pathogen that can harbor transferable resistance genes.
• Understanding the genetic context of resistance genes is crucial for combating antimicrobial resistance.

Purpose of the Study:

• To characterize the genetic environments of the plasmid-mediated blaCTX-M-3 gene in cefotaxime-resistant Serratia marcescens.
• To identify and describe the different genetic architectures associated with the blaCTX-M-3 gene.
• To report a novel complex class 1 integron in Serratia marcescens isolates from Taiwan.

Main Methods:

• Polymerase Chain Reaction (PCR) was used to amplify genetic regions.
• BLAST DNA sequence analysis was employed to identify gene sequences and their arrangements.
• Comparative analysis of genetic structures surrounding the blaCTX-M-3 gene was performed.

Main Results:

• Three distinct genetic architectures were identified in the regions surrounding the blaCTX-M-3 gene.
• Type I architecture featured tnpA-ISEcp1 insertion sequence and a reverse IS26 sequence upstream, with orf477 downstream.
• A novel complex class 1 integron containing the dfrA19 gene, flanked by class 1 integrons, was identified upstream of the blaCTX-M-3 gene.

Conclusions:

• The study elucidated the diverse genetic landscapes associated with the blaCTX-M-3 gene in Serratia marcescens.
• The identification of a novel complex class 1 integron carrying the dfrA19 gene in Taiwanese S. marcescens is a significant finding.
• These findings contribute to understanding the dissemination mechanisms of antimicrobial resistance genes in clinical settings.