Marcos Sergio Endo
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Fernanda Graziela Corrêa Signoretti
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Vivian Sayuri Kitayama
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Ariane Cássia Salustiano Marinho
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Frederico Canato Martinho
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<p><strong>Objective: </strong>The aim of this study was to evaluate the minimal inhibitory concentrations (MIC) of different antibiotic agents against to the most prevalent microorganism found in root-filled canals by culture and molecular approaches. <strong>Material and </strong><strong>Methods: </strong>The microbial samples were taken either from thirty root-filled canals after removal of gutta-percha. Culture methods and 16s rDNA assay were used to identify the <em>E faecails</em> present in the samples. The antimicrobial susceptibilities of the isolates of <em>E faecalis </em>were determined by MIC values using the E test System and interpreted according to the Clinical and Laboratory Standards Institute guidelines. The following antibiotics were used: benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin, rifampicin and moxifloxacin. <strong>Results: </strong><em>E faecalis</em> were isolated (7/30) and detected (13/30) by culture and PCR assay, respectively. All tested <em>E faecalis</em> (<em>n</em>=12) were highly sensitive to amoxicillin, moxifloxacin, vancomycin, benzylpenicillin and amoxicillin-clavulanic acid. Some antibiotics were resistant against <em>E faecalis </em>strains such as rifampicin (4/12), tetracycline (2/12), doxycycline (1/12), erythromycin (3/12) and azythromycin (8/12). <strong>Conclusion</strong>: Amoxicillin, amoxicillin-clavulanic acid, benzylpenicillin, vancomycin and moxifloxacin were the most active antibiotics, in vitro, against <em>E faecalis</em> clinical strains, with all the isolates being susceptible. Azithromycin and erythromycin were least effective, with none percentage of isolates being susceptible, during laboratory testing. Moreover, <em>E faecalis </em>were identified more frequently by PCR assay than by culture technique.</p><p><strong>Keywords: </strong>Retreatment; Antibiotics, antimicrobial susceptibility; <em>Enterococcus faecalis;</em> Antibiotic resistance. </p>