Profiling Antibiotic Susceptibility among Distinct Enterococcus faecalis Isolates from Dental Root Canals

Area of Science:

• Microbiology
• Infectious Diseases
• Dental Research

Background:

• Enterococcus faecalis is a major cause of hospital-acquired infections and frequently found in persistent root canal infections.
• The oral cavity may serve as a reservoir for multidrug-resistant Enterococcus faecalis strains.
• Antimicrobial susceptibility testing (AST) data for oral enterococci is limited.

Purpose of the Study:

• To investigate the antimicrobial susceptibility profiles of Enterococcus faecalis strains isolated from the oral cavity.
• To assess resistance patterns to key antibiotics, including first-line and last-resort agents.
• To highlight the importance of AST in dental settings for monitoring antimicrobial resistance.

Main Methods:

• Collected 37 Enterococcus faecalis strains: 34 endodontic isolates, 2 vanA-type vancomycin-resistant isolates, and 1 reference strain.
• Determined Minimum Inhibitory Concentrations (MICs) using Etest gradient strips against amoxicillin, vancomycin, clindamycin, tigecycline, linezolid, and daptomycin.
• Interpreted results based on established EUCAST (European Committee on Antimicrobial Susceptibility Testing) standards.

Main Results:

• Most endodontic isolates were susceptible to amoxicillin and vancomycin.
• A significant proportion of isolates exhibited intrinsic resistance to clindamycin.
• MICs for tigecycline and linezolid approached susceptibility breakpoints in some isolates, and vanA isolates were resistant to vancomycin and tigecycline.

Conclusions:

• While many oral Enterococcus faecalis strains remain susceptible to primary antibiotics, intrinsic clindamycin resistance is notable.
• The emergence of tigecycline resistance in vanA isolates underscores the potential for multidrug resistance acquisition in clinical strains.
• Routine AST implementation in dental practices is crucial for ongoing antimicrobial resistance surveillance.