Distribution of Rothia species in root canals in a Japanese population

Rothia species are components of the normal oral microflora, which have been recognized as emerging opportunistic pathogens in immune compromised hosts. This study was performed to investigate the distribution of Rothia species in infected root canals. The correlations of clinical findings with the presence of Rothia species were also evaluated. A total of 200 root canal samples, including 92 primary infections and 108 secondary infections, were collected from 200 Japanese patients. Polymerase chain reaction (PCR) targeting the 16S rRNA gene was performed to detect three Rothia species, i.e., Rothia mucilaginosa, Rothia aeria, and Rothia dentocariosa. The detection frequencies of R. mucilaginosa, R. aeria, and R. dentocariosa were 49/200 (24.5%), 95/200 (47.5%), and 55/200 (27.5%), respectively. There were no significant differences in the detection frequencies between primary and secondary endodontic infections. The detection frequency of R. mucilaginosa in cases with gingival swelling was 42.9%, and there were significantly more cases positive than negative for this species (P = 0.042). The presence of R. aeria also showed correlations with radiolucency around the root apex (P = 0.001) and pain on percussion (P = 0.044). Quantitative real-time PCR revealed that the relative abundance of R. mucilaginosa in total bacterial counts ranged from 0.04% to 91.8%. These results indicated that Rothia species colonize root canals at relatively high frequency, and that root canals are potential reservoirs of these pathogens. The results also suggest that Rothia species are involved in the pathogenesis of apical periodontitis.