title: The origin of endodontic Enterococcus faecalis explored by comparison of virulence factor patterns and antibiotic resistance to that of isolates from stool samples, blood cultures and food.
abstract: OBJECTIVE
  To elucidate the origin of Enterococcus faecalis isolated from secondary root canal infections and the possibility for a foodborne transmission by comparing them to strains recovered from food, blood and stool regarding putative virulence factors and antibiotic susceptibility profiles, where strains from common origin were hypothesized to harbour similar characteristics.
  
  
  METHODS
  A total of 108 E. faecalis strains recovered in the county of Stockholm, Sweden, were screened using PCR for putative virulence factors esp, cylA, gelE/gelatinase-negative phenotype (ef1841/fsrC), efaA, ace and asa1. The minimum inhibitory concentration (MIC) for ampicillin, piperacillin-tazobactam, imipenem, gentamicin, vancomycin, ciprofloxacin and linezolid was determined using the agar dilution method.
  
  
  RESULTS
  Next to strains from blood, the food isolates presented the highest average number of virulence determinants and were frequently enriched with asa1 coding for aggregation substance. None of the endodontic strains carried cylA, and the gelatinase-negative phenotype caused by a deletion dominated the group. Altogether, the most prevalent genes were gelE, efaA and ace, and a combination of them was equally present in approximately 80% of the strains from food, stool and root canals in comparison with 43.3% of the blood isolates. High-level resistance to ciprofloxacin and gentamicin was observed in 30% of the blood isolates, whereas the isolates from other origins, with single exceptions, were susceptible to all tested antibiotics.
  
  
  CONCLUSIONS
  Evidence for a foodborne transmission, explaining the high reported prevalence of E. faecalis in root filled teeth, could not be determined based on the similarities in virulence factor patterns and antibiotic susceptibility. The only linkage between isolates from food and root canals consisted of a shared common combination of the genes gelE, efaA and ace. The high occurrence of putative virulence traits in food isolates questions the safety of E. faecalis in food products.
authors.affiliation: Division of Endodontics, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Vidana
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Huddinge, Sweden.
authors.forename: M U
authors.initials: MU
authors.lastname: Rashid
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Huddinge, Sweden.
authors.forename: V
authors.initials: V
authors.lastname: Özenci
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Huddinge, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Weintraub
authors.affiliation: Division of Oral and Maxillofacial Surgery, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.|Department of Oral and Maxillofacial Surgery, Karolinska University Hospital, Huddinge, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Lund
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000071997:Blood Culture; D004352:Drug Resistance, Microbial; D013293:Enterococcus faecalis / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D005506:Food Contamination; D006801:Humans; D008826:Microbial Sensitivity Tests; D010485:Periapical Periodontitis / Q000382:microbiology*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011671:Pulpitis / Q000601:surgery; D012390:Root Canal Therapy; D013548:Sweden; D037521:Virulence Factors
chemical_list: D000900:Anti-Bacterial Agents; D037521:Virulence Factors
keywords: Enterococcus faecalis; antibiotic resistance; epidemiology; genotypic patterns; root canal infection; virulence factor