Antimicrobial susceptibility of Enterococcus faecalis isolated from canals of root filled teeth with periapical lesions

E. T. Pinheiro, B. P F A Gomes, D. B. Drucker, A. A. Zaia, C. C R Ferraz, F. J. Souza-Filho

    Research output: Contribution to journalArticlepeer-review


    Aim: To test, in vitro, the susceptibility to different antibiotics of Enterococcus faecalis isolates from canals of root filled teeth with periapical lesions. Methodology: Twenty-one E. faecalis isolates, from canals of root filled teeth with persisting periapical lesions, were tested for their antibiotic susceptibilities. The following antibiotics were used: benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin and moxifloxacin. Minimal inhibitory concentrations (MICs) for the antimicrobial agents were determined using the E-test System (AB BIODISK, Solna, Sweden), and the E. faecalis strains classified as susceptible or resistant according to the guidelines of National Committee for Clinical Laboratory Standards (NCCLS). The strains were also tested for β-lactamase production with nitrocefin (Oxoid, Basingstoke, UK). Results: All strains were susceptible to penicillins in vitro, however, the MICs of amoxicillin and amoxicillin-clavulanic acid (MIC90 = 0.75 μg mL-1) were lower than for benzylpenicillin (MIC90 = 3.0 μg mL-1). All strains studied were also susceptible to vancomycin and moxifloxacin, whilst 95.2% were susceptible to chloramphenicol. Amongst the isolates, 85.7% were susceptible to tetracycline and doxycycline and 80.9% to ciprofloxacin. The MIC of erythromycin ranged from 0.38 to >256 μg mL-1; only 28.5% of the strains were susceptible (MIC ≤ 0.5 μg mL-1). Limited susceptibility was also observed with azithromycin which was active against only 14.2% of isolates. No strains produced β-lactamase. Conclusion: Enterococcus faecalis isolates were completely susceptible, in vitro, to amoxicillin, amoxicillin-clavulanic acid, vancomycin and moxifloxacin. Most isolates were susceptible to chloramphenicol, tetracycline, doxycycline or ciprofloxacin. Erythromycin and azithromycin were least effective.
    Original languageEnglish
    Pages (from-to)756-763
    Number of pages7
    JournalInternational Endodontic Journal
    Issue number11
    Publication statusPublished - Nov 2004


    • Antimicrobial susceptibility
    • Endodontic failure
    • Enterococcus faecalis


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