Transferable resistance and aminoglycoside-modifying enzymes in enterococci

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Enterococci, including Streptococcus faecalis and S. faecium, are significant human pathogens.
• High-level aminoglycoside resistance (HLAR) in enterococci is a growing clinical concern, complicating treatment options.
• Understanding the mechanisms and transfer of HLAR is crucial for infection control.

Purpose of the Study:

• To investigate the patterns and mechanisms of aminoglycoside resistance in clinical isolates of S. faecalis and S. faecium.
• To determine the transferability of high-level aminoglycoside resistance between enterococcal strains.
• To identify the specific aminoglycoside-modifying enzymes responsible for high-level resistance.

Main Methods:

• Antibiotic susceptibility testing was performed on clinical isolates of S. faecalis and S. faecium.
• Filter membrane technique was used to assess the transfer of aminoglycoside resistance.
• Aminoglycoside-modifying enzymes were assayed using radiolabelled cofactors.

Main Results:

• Different patterns of high-level aminoglycoside resistance were observed among the isolates.
• Transfer of high-level aminoglycoside resistance was demonstrated between S. faecalis and S. faecium strains, including a previously undescribed transfer from S. faecalis to S. faecium.
• High-level gentamicin resistance was primarily attributed to the production of 2''-O-phosphotransferases, 3'-O-phosphotransferases, 6-O-adenylyltransferases, and 6'-N-acetyltransferases.

Conclusions:

• High-level aminoglycoside resistance in enterococci is mediated by a variety of aminoglycoside-modifying enzymes.
• The ability of these resistance traits to transfer between enterococcal species highlights the potential for rapid dissemination of antibiotic resistance.
• Novel transfer pathways underscore the need for continued surveillance and understanding of antimicrobial resistance mechanisms in clinical settings.