VanE-type vancomycin-resistant Enterococcus faecalis clinical isolates from Australia

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Enterococcus faecalis is a significant opportunistic pathogen.
• Vancomycin resistance in enterococci is a growing public health concern.
• The VanE type resistance mechanism requires further characterization.

Purpose of the Study:

• To investigate the molecular basis of VanE-type vancomycin resistance in three Enterococcus faecalis isolates from Australia.
• To analyze the expression patterns and transcriptional regulation of the vanE operon.

Main Methods:

• Phenotypic characterization of vancomycin resistance.
• Genetic analysis including sequencing of vanE operon genes.
• Gene expression analysis using techniques like RT-PCR or Northern blotting (implied).
• Transcription initiation site mapping.

Main Results:

• Three distinct Enterococcus faecalis VanE-type isolates (BM4574, BM4575, BM4576) were identified in Australia.
• Isolate BM4575 exhibited constitutive vanE gene expression, likely due to a 2-bp deletion in the vanSE gene.
• Isolates BM4574 and BM4576 displayed inducible vanE gene expression.
• Transcription analysis indicated that the five genes within the vanE operon are likely cotranscribed from a single promoter located upstream of the vanE gene.

Conclusions:

• The study elucidates the differential expression mechanisms of vanE-type resistance in Enterococcus faecalis.
• A specific genetic mutation (2-bp deletion in vanSE) can lead to constitutive resistance.
• The vanE operon is transcribed as a single unit, suggesting coordinated regulation of resistance genes.