How xylitol-containing products affect cariogenic bacteria.
BACKGROUND
The authors examined the effect of xylitol, a naturally occurring sweetener, on levels of Streptococcus mutans and S. sobrinus. They also investigated xylitol's mechanism of action.


METHODS
The authors compared cariogenic bacteria levels before and after exposure to xylitol products in children and adults. In the first study, 187 children received xylitol-containing snacks in school for four weeks. In the second study, two adults received xylitol candy for four weeks. Unstimulated saliva samples were taken from all subjects. Gingival samples also were taken from the adults. The authors plated the samples on selective microbiological media. Individual isolates were plated on media with varying concentrations of xylitol, and were identified using specific DNA probes. Genetic relatedness was determined via pulse-field gel electrophoresis.


RESULTS
The children's salivary S. mutans levels remained stable before and after xylitol exposure. Further analysis of the S. mutans isolates was conducted for seven children. Bacteria from five of these children grew with 10 percent or less xylitol at baseline, while the bacteria from all seven children grew with 15 percent xylitol after exposure to the xylitol-containing snacks, suggesting that the S. mutans increased in tolerance to xylitol during exposure. Six children had isolates with the same genotype at both time points. S. mutans and S. sobrinus levels were reduced in one of the adults as a result of xylitol exposure, and the bacterial isolates became more xylitol tolerant. In the second adult, S. mutans and S. sobrinus levels increased, while the subject maintained the same proportion of susceptible and tolerant strains as that at baseline.


CONCLUSIONS
Overall, consumption of xylitol-containing snacks and candy did not reduce S. mutans levels. However, bacteria from five children and one adult became more xylitol tolerant.


CONCLUSIONS
These results provide a basis on which xylitol-containing products can be recommended and xylitol's mechanism of action can be explained to patients.
Roberts
Marilyn C
MC
Department of Pathobiology, University of Washington, Seattle, USA.
Riedy
Christine A
CA
Coldwell
Susan E
SE
Nagahama
Sonia
S
Judge
Kathleen
K
Lam
Malinda
M
Kaakko
Tarja
T
Castillo
Jorge L
JL
Milgrom
Peter
P
D000328:Adult; D002182:Candy; D002327:Cariostatic Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial; D004361:Drug Tolerance; D005502:Food; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D013295:Streptococcus mutans / Q000187:drug effects* / Q000235:genetics; D016986:Streptococcus sobrinus / Q000187:drug effects* / Q000235:genetics; D014993:Xylitol / Q000494:pharmacology*
D002327:Cariostatic Agents; D014993:Xylitol