Identification of R plasmids mediating gentamicin resistance from Escherichia coli strains in Japan

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Parenteral infections pose significant clinical challenges.
• The emergence of antibiotic-resistant bacteria, particularly Escherichia coli, is a growing global health concern.
• Gentamicin resistance in E. coli can be mediated by plasmid-borne resistance genes.

Purpose of the Study:

• To identify and characterize gentamicin-resistant Escherichia coli strains isolated from parenteral infections.
• To investigate the genetic mechanisms underlying gentamicin resistance in these strains, focusing on R plasmids and associated enzymes.

Main Methods:

• Isolation and identification of E. coli strains from clinical samples.
• Antimicrobial susceptibility testing, including resistance profiling.
• Plasmid analysis to identify R plasmids mediating resistance.
• Enzyme characterization to identify aminoglycoside-modifying enzymes.

Main Results:

• Eight gentamicin-resistant E. coli strains were isolated from 630 E. coli strains.
• All eight resistant strains exhibited multiple drug resistance.
• These strains harbored R plasmids responsible for mediating gentamicin resistance.
• The identified R plasmids encoded two types of aminoglycoside-inactivating enzymes: AAD (2") and APH (3").

Conclusions:

• Gentamicin resistance in E. coli causing parenteral infections is often associated with multiply resistant strains carrying R plasmids.
• The presence of R plasmids specifying AAD (2") and APH (3") enzymes contributes significantly to gentamicin resistance.
• Understanding these resistance mechanisms is crucial for effective treatment strategies and infection control.