[Arbitrarily primed-PCR detection of Streptococcus mutans and Streptococcus sobrinus in dental plaque of children with high dmft and no caries].
OBJECTIVE
To isolate and identify Streptococcus mutans (Sm) and Streptococcus sobrinus (Ss) in dental plaque of children with high dmft and no caries by selective medium, biochemical methods and arbitrarily primed-polymerase chain reaction (AP-PCR).


METHODS
A total of 401 3-4-year-old children from seven kindergartens were recruited using cluster sampling and their dental caries status were examined. From 30% of children with the highest dmft score (dmft >/= 5), 20 children were chosen randomly as test group and 20 age and gender-matched caries-free children were selected as control. Plaque samples were collected from buccal surfaces of the molars and plated onto TYCSB plate. Sm and Ss were primarily identified by colony morphology and biochemical characteristics. Then chromosomal DNA of the strains was isolated and Sm or Ss were confirmed by AP-PCR.


RESULTS
The proportion positive for Sm and Ss in children with high dmft was 100% and 40% respectively while that in caries-free children was 75% and 5% by AP-PCR analysis. The differences were statistically significant between the two groups.


CONCLUSIONS
The proportions positive for Sm and Ss detected by AP-PCR method were significantly higher in children with high dmft than in caries-free children and it is a risk factor for high dmft in deciduous teeth harboring Sm and Ss.
Zhi
Qing-hui
QH
Department of Dental Public Health, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
Lin
Huan-cai
HC
Zhang
Rong
R
Liao
Yi-dong
YD
Tu
Jia-zhen
JZ
D002675:Child, Preschool; D003731:Dental Caries / Q000382:microbiology*; D003773:Dental Plaque / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D013295:Streptococcus mutans / Q000235:genetics / Q000302:isolation & purification*; D016986:Streptococcus sobrinus / Q000235:genetics / Q000302:isolation & purification*