Antagonistic action of indigenous Streptococcus mutans strains

ABSTRACT

Dental caries is an infectious process which ultimately destroys the tooth. Streptococcus mutans is considered to be the main agent causing this disease. If microorganisms with antagonistic action on S. mutans were found, they might provide a way of avoiding or controlling the disease. Within the framework of the Oral Microbial Ecology approach, the aim of this project was to identify S. mutans strains with antagonistic effect upon S. mutans. Saliva samples were taken from 66 children and cultured on Blood agar and Mitis Salivarius Bacitracin agar. They were incubated at 37oC in anaerobic atmosphere for 48 hours, after which bacteria were counted and biochemical tests performed on colonies compatible with S. mutans. Antagonistic effect was determined using the double layer in agar technique. In children without and with caries, the frequency of S. mutans was 91.7% and 96.7%, respectively. In the group of patients without caries, only two strains had no antagonistic action, and three strains had full antagonistic action (100%), while the rest showed different kinds of inhibitory action. In the group of patients with caries, only 5 strains had no antagonistic action, 32 strains had full antagonistic action (100%) and the rest had variable inhibitory action. To conclude, 112 S. mutans strains with high antagonistic potential were identified, which, after other requirements are fulfilled, could be used in caries prevention or control strategies.

RESUMEN

La caries dental es un proceso infeccioso que termina en la destruccion del diente. Streptococcus mutans es considerado el principal agente causal de esta enfermedad. La busqueda de microorganismos con accion antagonica sobre S. mutans puede ser una alternativa con la cual se pueda evitar o controlar esta enfermedad. Este proyecto enmarcado dentro de la linea de Ecologia Microbiana Oral, tuvo como objetivo identificar cepas S. mutans con efecto antagonico. Se tomaron muestras de saliva en 66 ninos y se cultivaron en Agar Sangre y Agar Mitis Salivarius Bacitracina. Despues de la incubacion a 37oC en anaerobiosis durante 48 horas, se hizo el recuento bacteriano y las colonias compatibles con S. mutans fueron sometidas a pruebas bioquimicas. La determinacion del efecto antagonico se realizo utilizando la tecnica de doble capa en agar. En los ninos sin caries y con caries la frecuencia de S. mutans fue, respectivamente, 91.7% y 96.7%. En el grupo de pacientes sin caries solo dos cepas no tuvieron ninguna accion antagonica, tres cepas tuvieron accion antagonica completa (100%), y las restantes presentaron diferentes modalidades de inhibicion. En el grupo de pacientes con caries solo 5 cepas no tuvieron ninguna accion antagonica, 32 cepas tuvieron accion antagonica completa (100%) y las demas cepas tuvieron actividad inhibitoria variable. En conclusion, se identificaron 112 cepas S. mutans con gran potencial antagonico, las cuales despues de cumplir con otros requerimientos podrian ser utilizadas en estrategias de prevencion o control de la caries dental.