Contribution of the Collagen-Binding Proteins of Streptococcus mutans to Bacterial Colonization of Inflamed Dental Pulp.

Ryota Nomura,Yuko Ogaya,Kazuhiko Nakano,Z Tom Wen

doi:10.1371/journal.pone.0159613

Abstract

Streptococcus mutans is a major pathogen of dental caries. Collagen-binding proteins (CBPs) (approximately 120 kDa), termed Cnm and Cbm, are regarded as important cell surface antigens related to the adherence of S. mutans to collagenous tissue. Furthermore, CBP-positive S. mutans strains are associated with various systemic diseases involving bacteremia, such as infective endocarditis. Endodontic infection is considered to be an important cause of bacteremia, but little is known regarding the presence of S. mutans in dental pulp tissue. In the present study, the distribution and virulence of S. mutans in dental pulp tissues were investigated by focusing on CBPs. Adhesion and invasion properties of various S. mutans strains were analyzed using human dental pulp fibroblasts (HDPFs). CBP-positive strains had a significantly higher rate of adhesion to HDPFs compared with CBP-defective isogenic mutant strains (P<0.001). In addition, CBP-positive strains induced HDPF proliferation, which is a possible mechanism related to development of hyperplastic pulpitis. The distribution of S. mutans strains isolated from infected root canal specimens was then analyzed by PCR. We found that approximately 50% of the root canal specimens were positive for S. mutans. Approximately 20% of these strains were Cnm-positive, while no Cbm-positive strains were isolated. The Cnm-positive strains isolated from the specimens showed adhesion to HDPFs. Our results suggest that CBP-positive S. mutans strains exhibit high colonization in dental pulp. This could be a possible virulence factor for various systemic diseases.

Highlights

Streptococcus mutans is a major pathogen of dental caries and is regarded as a causative agent of infective endocarditis [1]
The rates of adhesion to and invasion of human dental pulp fibroblasts (HDPFs) isolated from primary teeth for the TW295 (Cnm-positive) and NN2193-1 (Cbm-positive) strains were significantly higher compared with their Cnm- and Cbm-defective isogenic mutant strains, respectively, and other Collagen-binding proteins (CBPs)-negative strains (P
CBP-positive S. mutans strains did not cause prominent proliferation of HDPFs isolated from permanent teeth, there was significantly greater proliferation in CBP-positive strains compared with CBP-negative strains (P

Summary

Introduction

Streptococcus mutans is a major pathogen of dental caries and is regarded as a causative agent of infective endocarditis [1]. Collagen-binding proteins (CBPs) of approximately 120 kDa, termed Cnm and Cbm, in S. mutans have been characterized as LPXTG-anchored cell surface proteins [2, 3]. Cnm and Cbm have a frequency of distribution in S. mutans oral strains of approximately 10–20% and 2%, respectively [3, 4]. Bacterial DNA of CBP-positive S. mutans strains was detected in cardiovascular specimens at a high frequency [5]. In vitro and in vivo findings have demonstrated that these strains are PLOS ONE | DOI:10.1371/journal.pone.0159613. In vitro and in vivo findings have demonstrated that these strains are PLOS ONE | DOI:10.1371/journal.pone.0159613 July 21, 2016

Methods

Results

Conclusion