[The relationship in growth between A.actinomycetemcomitans and cariogenic bacteria in vitro].
OBJECTIVE
To investigate the correlation in growth between A.actinomycetemcomitans and cariogenic bacteria of S.mutans, L.acidophilus A.naeslundii A.viscosus in vitro.


METHODS
Using improvement agar diffusion method and dual-species (A.actinomycetemcomitans with each of cariogenic bacteria) incubation in BHI broth, we studied the relationship between A.actinomycetemcomitans and 4 kinds cariogenic bacteria in growth. The characteristic and percentage of A.actinomycetemcomitans in dual-species biofilms were detected with SEM and CFU(colony forming units).The data were analyzed for significance using an independent two-sample t test with SPSS 10.0 software package.


RESULTS
The agar diffusion essay showed that A.actinomycetemcomitans had no effect on the growth of S.mutans, L.acidophilus A.naeslundii and A.viscosus. While these 4 kinds of cariogenic bacteria could inhibit the growth of A.actinomycetemcomitans. The ratio of A.actinomycetemcomitans in the dual-species suspension decreased gradually.In dual-species BHI broth, the proportion of A.actinomycetemcomitans cultured alone ahead of 12 hours decreased as well, which came to 0 at 24-hour in S.mutans and L.acidophilus groups. There was significant difference between different time groups(P<0.05).The single A.actinomycetemcomitans was failed to form three-dimensional biofilm and just a small quantity of cells accumulated and adhered. On the contrary, the 4 kinds of single cariogenic bacteria could form mature biofilms respectively by themselves at 48-hour,of which the appearance of biofilms had no apparent change to that of single cariogenic bacteria after mixing A.actinomycetemcomitans. CFU of dual-species biofilms indicated that the percentage of A.actinomycetemcomitans in biofilms decreased gradually by changing medium per 12 hours. There were significant difference among the three time spots(P<0.05).


CONCLUSIONS
The study shows that S.mutans, L.acidophilus A.naeslundii and A.viscosus could inhibit the growth of A.actinomycetemcomitans in vitro.
Han
Yao-Lun
YL
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041, Sichuan Province, China.
Hao
Yu-Qing
YQ
Zhang
Chao-Liang
CL
Lu
Jun-Jun
JJ
D001419:Bacteria; D018441:Biofilms; D003731:Dental Caries; D006801:Humans; D066298:In Vitro Techniques; D013295:Streptococcus mutans