Effect of endodontic procedures on enterococci, enteric bacteria and yeasts in primary endodontic infections

To detect enterococci, enteric bacteria and yeast species from the canals of teeth with primary endodontic infections before and after canal preparation and to test the antibiotic susceptibility of enterococcal strains isolated from infected root canals.

Twenty-five single-rooted teeth with pulp necrosis, intact pulp chambers and periradicular lesions were selected for study. Samples were collected from canals before and after instrumentation. Amongst isolated microorganisms from infected root canals only enterococci, enteric bacteria and yeasts were identified by biochemical tests. The in vitro antimicrobial susceptibility of isolated enterococci strains was evaluated by the Etest system.

Microorganisms were isolated from 92% of the samples following intracoronal access, 22% were enterococci, enteric bacteria or yeast species. After biomechanical preparation, these species were no longer detected. After 7 days without intracanal dressing, 100% of the canals contained microorganisms, 52% of which were target species. However, after using paramonochlorophenol [PRP (2.0 g), Rinosoro and polyethylene glycol (400 equal parts up to 100 mL)] as an intracanal dressing for 7 days, enteric bacteria and yeasts were not detected; only enterococci were still present. All strains of enterococci were susceptible to ampicillin, but exhibited variable susceptibility to rifampin and ciprofloxacin.

Enterococci, enteric bacteria and yeasts were present in primary endodontic infections. Enterococci, particularly Enterococcus faecalis and E. faecium were resistant to removal by root canal preparation followed by intracanal dressing.