Identical genes confer high-level resistance to gentamicin upon Enterococcus faecalis, Enterococcus faecium, and...

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• High-level gentamicin resistance (HLGR) is a significant clinical concern.
• The bifunctional enzyme 6 extquotesingle-acetyltransferase-2 extquotesingle extquotesingle-phosphotransferase (6 extquotesingleAAC-2 extquotesingleAPH) confers HLGR.
• Understanding the genetic basis of HLGR is crucial for combating antibiotic resistance.

Purpose of the Study:

• To identify and characterize the structural gene encoding the 6 extquotesingleAAC-2 extquotesingleAPH enzyme.
• To investigate the presence and homology of this gene in clinical isolates of enterococci and Streptococcus agalactiae.
• To develop a method for distinguishing resistant from susceptible strains.

Main Methods:

• Polymerase chain reaction (PCR) amplification of the target gene.
• DNA hybridization assays using nonradioactively labeled oligonucleotide probes (dot blot).
• Analysis of clinical isolates of Enterococcus faecalis, Enterococcus faecium, and Streptococcus agalactiae.

Main Results:

• The structural gene for 6 extquotesingleAAC-2 extquotesingleAPH was successfully amplified from clinical isolates.
• Genes encoding this antibiotic resistance trait showed high homology across Enterococcus and Streptococcus species.
• Dot blot hybridization unequivocally differentiated between HLGR and non-HLGR strains.
• Both 6 extquotesingle-acetylating and 2 extquotesingle-phosphorylating gene segments were present in all HLGR isolates.

Conclusions:

• The 6 extquotesingleAAC-2 extquotesingleAPH gene is a conserved genetic determinant of high-level gentamicin resistance in enterococci and Streptococcus agalactiae.
• PCR and dot blot hybridization are effective tools for detecting this resistance mechanism.
• The findings contribute to understanding the molecular epidemiology of gentamicin resistance.