Isolation and characterization of Streptococcus mutans in heart valve and dental plaque specimens from a patient with infective endocarditis

Abstract

Streptococcus mutans, known to be an aetiologic agent of dental caries, also causes infective endocarditis (IE), although a comparison of isolates from the oral cavity and infected heart valve of the same patient has not been reported. In the present study, infected heart valve and dental plaque samples from a patient with IE were analysed. Broad-range PCR with DNA sequencing revealed that 50 clones from the dental plaque isolates were composed of oral streptococci and periodontopathic bacteria, whereas only Streptococcus mutans was detected in 50 clones from the heart valve. Eighteen strains of Streptococcus mutans were isolated from dental plaque and seven from the heart valve, and the biochemical properties of each were in accordance with those of Streptococcus mutans. DNA fingerprinting analysis revealed that all the oral isolates of Streptococcus mutans had similar patterns, which were different from those of the isolates from the infected heart valve. Western blotting using glucosyltransferase (GTF)-specific antiserum showed that the seven strains from the heart valve lacked the three types of intact GTF. In addition, the sucrose-dependent adhesion rates of these isolates were significantly lower than those of the oral isolates (P<0?001). Furthermore, the isolates from the heart valve were less susceptible to erythromycin and kanamycin. These results indicate that the properties of the Streptococcus mutans strains isolated from the infected valve were different from those of typical oral strains, which may be related to the effects of IE. INTRODUCTIONOral streptococci, which are major members of oral flora, frequently cause bacteraemia and infective endocarditis (IE) (Douglas et al., 1993). In 26 studies published between 1993 and 2003, 3784 cases of IE were presented, in which oral streptococci were considered to be involved in 21 %, second highest in frequency to Staphylococcus aureus (Moreillon & Que, 2004). According to a review of 848 IE cases in Japan, the most common type of micro-organism isolated from patient samples was Gram-positive streptococci (93?1 %), among which oral streptococci were frequently detected at a prevalence of 38?6 % (Nakatani et al., 2003). Streptococcus mutans, a major cause of dental caries, has occasionally been isolated from the blood of patients with IE and several case reports regarding the association of Streptococcus mutans and IE have been presented (Vose et al., 1987;Ullman et al., 1988;Gauduchon et al., 2001).The complete genome of Streptococcus mutans strain UA159 has been sequenced and was shown to be composed of approximately 2 million base pairs containing nearly 2000 open reading frames (Ajdić et al., 2002). Among them, three types of glucosyltransferase (GtfB, GtfC and GtfD) and protein antigen c (PAc) are known to be major cell surface proteins. In the case of IE, GtfB, GtfC and GtfD are known to induce the production of cytokines, such as interleukin-6 (IL-6) from monocytes (Shun et al., 2005). Several reports have discussed the association of PAc with IE, a...

Multilocus sequence typing analysis of Streptococcus mutans strains with the cnm gene encoding collagen-binding adhesin

“…The detection of S. mutans in specimens taken from patients with IE has been reported by either conventional or molecular techniques (Gauduchon et al, 2001;Nakano et al, 2006;Nomura et al, 2006;Vose et al, 1987;Ullman et al, 1988). Since IE is initiated by the colonization of the organism on the ECM of damaged endothelium in heart tissue (Moreillon & Que, 2004), bacterial molecules associated with adhesion to ECM are considered important.…”

“…Various pieces of evidence show the association of S. mutans with some life-threatening diseases such as infective endocarditis (IE), although the major species related to IE belong to the mitis group of oral streptococci (Banas, 2004;Mylonakis & Calderwood, 2001). Moreover, continuous detections of this bacterium in specimens from patients suffering from such disease emphasize the importance of S. mutans in IE (Gauduchon et al, 2001;Nomura et al, 2006;Vose et al, 1987;Ullman et al, 1988). Indeed, studies to clarify specific components involved in IE in S. mutans have also been performed worldwide (Beg et al, 2002;Jung et al, 2009; MatsumotoNakano et al, 2009;Miller-Torbert et al, 2008).…”

Molecular characterization of Streptococcus mutans strains isolated from the heart valve of an infective endocarditis patient

“…Examination of blood isolates of S. mutans from patients with bacteraemia or IE has been reported in several studies in which alterations of cell-surface components such as serotype-specific polysaccharides or protein antigens were described (Munro & Macrina, 1993;Fujiwara et al, 2001;Chia et al, 2004;Nomura et al, 2006Nomura et al, , 2007Nakano et al, 2007). For GTFs, analysis of an S. mutans isogenic mutant strain with defects in the three types of GTF generated from the blood isolate strain V403 showed that sucrose-derived exopolysaccharides contributed to infectivity in endocarditis caused by S. mutans (Munro & Macrina, 1993).…”

“…Table 1 summarizes the S. mutans strains used in this study. Strains V1-V7 and P1-P18 were isolated from heart valve and dental plaque specimens, respectively, obtained from an IE patient (Nomura et al, 2006). Strain MT8148 and its isogenic mutant strains defective in GTF expression (S2, R4, DE1, S5, B9, C13 and BC7s) were also used (Ooshima et al, 2001).…”

“…We previously isolated S. mutans strains (including strain V1) that did not express GTFs from an IE patient (Nomura et al, 2006). The colony morphology of these strains on agar plates was apparently different from that of typical S. mutans strains, whereas it was similar to strains generated by inactivation of the genes encoding GTFs (Ooshima et al, 2001).…”