Cultivable Anaerobic Microbiota of Infected Root Canals With/Without Marginal Leakage

Objectives: Apical periodontitis is an infectious and inflammatory disease of the periapical tissues caused by oral bacteria invading the root canal system. We reported the majority of the intracanal-microbiota was obligate anaerobes (Sato, Yamaki et al 2012). However, the environment within the canal might be affected by the degree of its coronal seal. The aims of this study were to profile the microbiota in infected root canals with coronal leakage, and to compare them with those without obvious marginal leakage.
Methods: After obtaining informed consent, samples were collected from 4 infected root canals with periapical lesion and cultured anaerobically for 7 days on CDC blood agar plates. All canals were exposed to the oral cavity because of caries and lack of coronal seal. Colony forming units (CFU) were counted and isolated bacteria were identified by 16S rRNA gene sequencing.
Results: The mean bacterial count (CFU) in these 4 canals was (3.3 ± 6.5) x 10⁴ (Range 2.0 x 10¹ - 1.3 x 10⁵). All isolates were facultative anaerobes, and no obligate anaerobes were found to be isolated. The predominant isolates were Lactobacillus (81.5%; L. crispatus, L. fermentum, L. johnsonii/gasseri, L. plantarum and L. rhamnosus) and Enterococcus (18.5%; E. faecalis).
Conclusions: The bacteria isolated predominantly from canals with coronal leakage were facultative anaerobes (Lactobacillus and Enterococcus). The majority of the microbiota in root canals without obvious marginal leakage was reportedly obligate anaerobes (Olsenella, Mogibacterium, Pseudoramibacter, Propionibacterium and Parvimonas). These findings suggest that the environment in root canals with leakage is clearly distinct from those without leakage, and that the latter root canals specifically support the growth of obligate anaerobes.