Diversity in endodontic Enterococcus faecalis from Brazil with high occurrence of ST 397 clone

Abstract

Objectives: The aim of this study was to assess the genetic relatedness of E. faecalis strains from primary endodontic infections in Brazil, test the hypothesis of clones infecting unrelated individuals, and examine the antimicrobial resistance profile. Materials and Methods: The genetic relationship of 32 endodontic E. faecalis were investigated by multilocus sequecing typing (MLST). These isolates were collected from unrelated patients with primary endodontic infection treated in Brazil between 2010 and 2023. Antimicrobial susceptibility testing was performed using the disk diffusion technique according to the Clinical Laboratory Standard Institute. Results: 12 sequence types (STs) were detected, of which 8 STs contained only one strain. We found clones of ST 30, ST40, ST 97 and ST 397, with a high frequency of the latter (15/32). Susceptibility to the antimicrobial agents tested varied, with the highest percentage of resistance observed for clindamycin (100%), tetracycline (34.4%), azithromycin (31.2%) and ciprofloxacin (19.2%). One isolate was multidrug resistant. Conclusions: MLST of endodontic E. faecalis showed clones infecting different individuals in different cities up to 10 years apart with high occurrence of ST 397. This data, together with the literature, raise the concern that there may be clones specialized in endodontic infections. Further MLST studies are needed, as well as surveillance for antimicrobial resistance in endodontic isolates. Clinical Relevance: Enterococcus faecalis is a common cause of nosocomial infections and is frequently associated with root canal infections. The identification of clones specialized in endodontic infections may lead to more effective therapeutic strategies.