Antibiotic Resistance Genes and Antibiotic Susceptibility of Oral Enterococcus faecalis Isolates Compared to Isolates from Hospitalized Patients and Food

  • Annette Carola Anderson
  • Huria Andisha
  • Elmar Hellwig
  • Daniel Jonas
  • Kirstin Vach
  • Ali Al-Ahmad
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 1057)


Enterococcus faecalis, a commensal of the intestinal tract of humans and animals is of great significance as leading opportunistic pathogen, and also prevalent in oral diseases, such as endodontic infections, as well as the healthy oral cavity. To investigate the potential of oral E. faecalis to constitute a reservoir of antibiotic resistance, isolates from supragingival plaque/saliva and from endodontic infections were screened regarding their resistance to selected antibiotics in comparison to nosocomial and food isolates.

70 E. faecalis isolates were analyzed with PCR regarding their equipment with the resistance genes tetM, tetO, ermB, ermC, vanA, vanB and blaTEM. Additionally, they were tested for their phenotypic resistance to doxycycline, azithromycin, rifampicin, amoxicillin and streptomycin using the Etest.

High percentages of the plaque/saliva, nosocomial and food isolates were resistant to doxycycline and azithromycin, particularly plaque/saliva isolates (81%) and nosocomial isolates (73.3%) showed resistance to doxycycline, significantly more than among the food and endodontic isolates. Rifampicin resistance was widespread among isolates from plaque/saliva (52.4%), endodontic infections (50%) and nosocomial infections (40%); all isolates were susceptible to amoxicillin and all oral isolates to high-level streptomycin. TetM genes were detected in the majority of all isolates and ermB genes were present in many nosocomial and plaque/saliva isolates. Thirty percent of the endodontic isolates and 53% of the nosocomial isolates were equipped with blaTEM genes.

The results suggest that the oral cavity can harbor E. faecalis strains with multiple resistances against different antibiotics and thus be regarded as a potential source of resistance traits.


Antibiotic resistance Endodontic infections Enterococci Food Nosocomial infections Oral cavity Plaque 



The authors thank Bettina Spitzmüller, Kristina Kollmar and Annette Wittmer for excellent technical assistance and Nicole Arweiler, Daniel Jonas and Ingrid Huber for providing part of the isolates, as well as Grant Anderson for English language correction.

Conflicts of Interest

The authors deny any conflicts of interest related to this study.

Ethical Statement

All endodontic and clinical isolates were obtained after approval by the Ethics Committee (no. 140/09, University of Freiburg).


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • Annette Carola Anderson
    • 1
  • Huria Andisha
    • 1
  • Elmar Hellwig
    • 1
  • Daniel Jonas
    • 2
  • Kirstin Vach
    • 3
  • Ali Al-Ahmad
    • 1
  1. 1.Department of Operative Dentistry and Periodontology, Medical Center - University of Freiburg, Faculty of MedicineUniversity of FreiburgFreiburgGermany
  2. 2.Institute for Environmental Health Sciences and Hospital Infection ControlMedical Center - University of Freiburg, Faculty of Medicine, University of FreiburgFreiburgGermany
  3. 3.Center for Medical Biometry and Medical Informatics, Institute for Medical Biometry and Statistics, Medical Center - University of Freiburg, Faculty of MedicineUniversity of FreiburgFreiburgGermany

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