Tn5381, a conjugative transposon identifiable as a circular form in Enterococcus faecalis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Multiply resistant Enterococcus faecalis strains harbor mobile genetic elements.
• Conjugative transposons play a significant role in the dissemination of antibiotic resistance genes.

Purpose of the Study:

• To identify and characterize novel conjugative transposons in Enterococcus faecalis.
• To investigate the transfer mechanisms and regulation of these transposons.

Main Methods:

• Identification of 19-kb conjugative transposons (Tn5381, Tn5383) via hybridization studies.
• Assessment of chromosomal and plasmid integration capabilities in a Rec- environment.
• Determination of inter-strain transfer frequencies under various growth conditions.
• Analysis of transposon circularization using agarose gel electrophoresis and hybridization.

Main Results:

• Tn5381 and Tn5383 confer resistance to tetracycline and minocycline through the tetM gene.
• These transposons integrate into the chromosome or plasmids and transfer between strains at varying frequencies.
• A circularized form of Tn5381 was identified in E. faecalis, a phenomenon previously observed only in E. coli.
• Subinhibitory tetracycline concentrations increased Tn5381 transfer frequency and circular form abundance.

Conclusions:

• Tn5381 is a Tn916-related conjugative transposon.
• The conjugative transfer and circularization of Tn5381 appear to be regulated by tetracycline presence.
• These findings provide insights into the mobile nature of antibiotic resistance in Enterococcus faecalis.