The aim of this study was to investigate the prevalence of virulence factors and the antimicrobial resistance of Enterococcus faecalis isolates of teeth with failure of the endodontic treatment. Methods Twenty root canal samples were collected from teeth with apical periodontitis. E. faecalis was...

The aim of this study was to investigate the prevalence of virulence factors and the antimicrobial resistance of Enterococcus faecalis isolates of teeth with failure of the endodontic treatment. Methods Twenty root canal samples were collected from teeth with apical periodontitis. E. faecalis was firstly identified based on phenotypic features and then by 16S ribosomal RNA gene sequencing. The antimicrobial susceptibility was determined by the minimum inhibitory concentration (MIC) of amoxicillin, amoxicillin + clavulanate, azithromycin, benzylpenicillin, ciprofloxacin, clindamycin, chloramphenicol, doxycycline, erythromycin, gentamicin, metronidazole, moxifloxacin, rifampicin, tetracycline, and vancomycin using the E test method. Virulence factors (ace, asa, asa373, cylA, efaA, esp, and gelE) were detected by polymerase chain reaction assay. Results Amoxicillin + clavulanate was effective against all strains. Intermediate and total resistance was found against the majority of the tested antimicrobials. The susceptibility of some microorganisms to some antimicrobial agents changed according to the evaluation time. MIC50 and MIC90 also varied according to the evaluation time. In relation to the virulence factors of the E faecalis isolates, ace was detected in 100% of the strains, asa (60%), asa373 (15%), efaA (95%), esp (70%), and gelE (75%), whereas cylA was not detected. Conclusions It was concluded that E. faecalis isolates from persistent endodontic infections showed varied degrees of intermediate/total resistance to several antimicrobial agents, with amoxicillin + clavulanate being the most effective agent. Moreover, the strains showed different patterns for virulence gene detection

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ

308162/2014-5

COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP

2012/23697-4

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