Isolation of Propionibacterium acnes among the microbiota of primary endodontic infections with and without intraoral communication

Abstract

Objectives: The presence of opportunistic pathogens such as Propionibacterium acnes (P. acnes) may contribute to the endodontic pathology. The presence of P. acnes may be influenced by different endodontic conditions. The aims of the study were firstly, to identify P. acnes within the whole cultivable microbiota of primary endodontic infections, to investigate which P. acnes phylotypes predominate in such infections and secondly to determine if the presence of an "open" communication (e.g. a sinus) can be associated with the isolation of P. acnes from the root canal.

Material and methods: The predominant cultivable microbiota of 15 primary endodontic lesions (7 without communication with the oral environment and 8 with an open communication) were identified using partial 16S ribosomal RNA (rRNA) gene sequence analysis. The identification of the organism was determined by interrogating the Human Oral Microbiome Database. The P. acnes isolates were typed on the basis of the recA gene sequence comparison. A neighbor-joining tree was constructed using MEGA 4.1 with the inclusion of known recA sequences.

Results: There was no difference in the number of species identified from lesions without communication (5.86 ± 3.7) and those with communication (5.37 ± 3.6) (P > 0.05). PCR-based 16S rRNA gene sequencing revealed P. acnes as the most prevalent isolate recovered from lesions with communication. recA gene sequencing revealed two phylogenetic lineages present in lesion with communication, with mainly type I (further split into type IA and type IB) and type II.

Conclusions: The presence of P. acnes as opportunistic pathogens has been confirmed and may sustain the traits observed in specific clinical presentations.

Clinical relevance: Clinical management of open lesions may require further disinfection to eliminate opportunistic bacteria.

Keywords: Endodontic disease; Fistula; Nosocomial infection; P. acnes.

Fig. 1

Prevalence of the 33 microbial taxa in 7 primary endodontic lesions without communications with the oral environment

Fig. 2

Phylogenetic tree showing all 33 bacterial taxa belonging to 3 phyla from 132 isolates identified from the 7 primary endodontic cases without communications. The tree was constructed by the neighbor-joining method based on 16S rRNA gene sequence comparisons. The scale bar represents 0.05 substitutions per nucleotide position. The numbers at the node of the tree indicate bootstrap values for each node out of 500 bootstrap resampling

Fig. 3

Prevalence of the 26 microbial taxa in 8 primary endodontic lesions with communications with the oral environment

Fig. 4

Phylogenetic tree showing all 26 bacterial taxa belonging to 5 phyla from 136 isolates identified from the 8 primary endodontic cases with communications. The tree was constructed by the neighbor-joining method based on 16S rRNA gene sequence comparisons. The scale bar represents 0.05 substitutions per nucleotide position. The numbers at the node of the tree indicate bootstrap values for each node out of 500 bootstrap resampling.

Fig. 5

Phylogenetic tree obtained by partial recA sequencing of 47 endodontic P. acnes isolates showing three distinct P. acnes phylotypes type IA, IB and II. Neighbor-joining (NJ) tree was constructed using the Jukes-Cantor method. The scale bar represents 0.05 substitutions per nucleotide position. The numbers at the node of the tree indicate bootstrap values for each node out of 500 bootstrap resampling