Food-borne enterococci integrate into oral biofilm: an in vivo study.
BACKGROUND
Enterococci, particularly Enterococcus faecalis, are still a primary concern in endodontic infections. To date, enterococci have been considered to be only transiently present in the oral cavity. The aim of this study was to examine whether different enterococci from food are able to reside in oral biofilm.


METHODS
Six healthy volunteers wore dental splints loaded with enamel slabs. After 3 days, the volunteers consumed cheese containing enterococci. The fate of the enterococci was analyzed by culture technique and 16S rRNA gene sequencing. All isolates were characterized genotypically by macrorestriction analysis (SmaI) and pulsed-field gel electrophoresis. E. faecalis was also analyzed by using fluorescent in situ hybridization (FISH).


RESULTS
E. faecalis, E. faecium, E. avium, and E. durans were detected in the initial biofilm after 2 hours, as well as in the 5-day-old oral biofilm. E. faecalis, E. faecium, and E. avium isolated from the initial biofilm and from the 5-day-old biofilm, as well as those isolated from cheese, showed genetic homogeneity. E. faecium and E. avium had integrated into a pre-existing 3-day-old biofilm. No genetic similarity between E. durans strains isolated from cheese and those from the initial and 5-day-old oral biofilm was detected. E. faecalis was also detected in the oral biofilm by using FISH.


CONCLUSIONS
Food-borne enterococci, particularly E. faecalis, might not only be transient but could also survive in the oral biofilm and become a source for endodontic infections. Moreover, genotypic analysis is required to study the source of oral enterococci.
Department of Operative Dentistry and Periodontology, Albert-Ludwigs-University, Freiburg, Germany. ali.al-ahmad@uniklinik-freiburg.de
Ali
A
Al-Ahmad
Julia
J
Maier
Marie
M
Follo
Bettina
B
Spitzmüller
Annette
A
Wittmer
Elmar
E
Hellwig
Johannes
J
Hübner
Daniel
D
Jonas
D000328:Adult; D000818:Animals; D001422:Bacterial Adhesion; D058491:Bacterial Load; D001431:Bacteriological Techniques; D018441:Biofilms; D002417:Cattle; D002611:Cheese / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis; D003743:Dental Enamel / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000145:classification / Q000502:physiology*; D013293:Enterococcus faecalis / Q000302:isolation & purification / Q000502:physiology; D016984:Enterococcus faecium / Q000302:isolation & purification / Q000502:physiology; D005516:Food Microbiology; D005838:Genotype; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D009055:Mouth / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012463:Saliva / Q000382:microbiology; D013997:Time Factors
D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S