Detection of Streptococcus mutans by PCR amplification of the spaP gene in teeth rendered caries free.
OBJECTIVE
To investigate the degree of association between tactile and optical criteria as used to assess the carious status of the enamel-dentine junction (EDJ) during cavity preparation, assessment with a caries detector dye and detection of Streptococcus mutans using culture and polymerase chain reaction (PCR) techniques.


METHODS
Twenty-nine teeth, extracted within the previous 30 min, and 15 teeth prepared under rubber dam in vivo, were clinically assessed at the EDJ after the removal of evident carious tissue. Demineralisation was then assessed using a caries detector dye (1% acid red in propylene glycol; Cavex). A rosehead bur was used to remove tissue at the EDJ for culture and PCR analysis. Culture was carried out on a tryptone yeast cystine sucrose bacitracin selective medium, and PCR used to amplify a sequence (192 bp) of the spaP gene, which encodes the surface protein antigen I/II of S. mutans.


RESULTS
Demineralised tissue at the EDJ, as shown using the dye, was found in 52% of teeth. Removed tissue was culture and PCR positive for S. mutans in 2 and 47% of teeth, respectively. A highly significant association (77% of cases; P < 0.001) was shown between dye and PCR assessment methods. No association was found between any other combination of assessment methods.


CONCLUSIONS
Culture methods may underestimate the presence of S. mutans. Removal of sufficient dye-stained tissue is therefore recommended to prevent further carious assault from residual S. mutans.
Department of Oral Microbiology, St. Bartholomew's, London, UK. R.P.Allaker@mds.qmw.ac.uk
R P
RP
Allaker
S V
SV
Seddon
C
C
Tredwin
E
E
Lynch
D000942:Antigens, Bacterial / Q000032:analysis / Q000235:genetics*; D000954:Antigens, Surface / Q000032:analysis / Q000235:genetics; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics*; D001431:Bacteriological Techniques; D001482:Base Composition; D001483:Base Sequence; D016009:Chi-Square Distribution; D015169:Colony Count, Microbial; D003470:Culture Media; D003731:Dental Caries / Q000175:diagnosis / Q000382:microbiology / Q000473:pathology / Q000628:therapy*; D003737:Dental Cavity Preparation; D003743:Dental Enamel / Q000382:microbiology / Q000473:pathology; D003793:Dental Restoration, Permanent; D003804:Dentin / Q000382:microbiology / Q000473:pathology; D000939:Epitopes / Q000032:analysis / Q000235:genetics*; D005456:Fluorescent Dyes; D005784:Gene Amplification; D006801:Humans; D008562:Membrane Glycoproteins; D016133:Polymerase Chain Reaction; D012235:Rhodamines; D013295:Streptococcus mutans / Q000235:genetics / Q000302:isolation & purification*; D017001:Tooth Demineralization / Q000175:diagnosis / Q000382:microbiology / Q000473:pathology; D014110:Touch
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D003470:Culture Media; D000939:Epitopes; D005456:Fluorescent Dyes; D008562:Membrane Glycoproteins; D012235:Rhodamines; C055764:S-layer proteins; C022027:lissamine rhodamine B