Antecedentes: la melatonina es una hormona producida en organismos vertebrados, invertebrados y plantas. Tiene importancia odontológica por su participación en procesos de oseointegración e inmunomodulación. Además, se ha reportado una posible actividad antibacteriana. Objetivo: evaluar el efecto antibacteriano de la melatonina sobre Streptococcus mutans CIO315, Staphylococcus aureus CIO613, Staphylococcus epidermidis CIO615 y Escherichia coli CIO465. Métodos: este estudio de diseño experimental se llevó a cabo con el método de dilución en agar Mueller-Hinton. Se evaluaron concentraciones de melatonina de 43 a 3 µM. De cada una de las cuatro bacterias se preparó una suspensión que se ajustó a la escala 0,5 de McFarland. Finalmente, sobre la superficie del agar se colocó 1 µl de cada bacteria y se incubó por 24 y 48 h a 37 °C. Resultados: la melatonina mostró un efecto antibacteriano frente a los cuatro microrganismos estudiados en una concentración de 43 µM a las 24 y 48 h. Conclusiones: la melatonina presenta una excelente actividad antimicrobiana sobre Streptococcus mutans CIO315, Staphylococcus aureus CIO613, Staphylococcus epidermidis CIO615 y Escherichia coli CIO465 en una concentración de 43 µM, lo que indica que se podría utilizar como una opción en la prevención y tratamiento de patologías orales como la caries dental y la periodontitis. Background: Melatonin is a hormone produced by vertebrate organisms, invertebrates, and plants. It is important in dentistry because it participates in osseointegration and immunomodulation processes. In addition, there are reports suggesting a possible antibacterial activity of melatonin. Purpose: To evaluate the antibacterial effect of melatonin on Streptococcus mutans CIO315, Staphylococcus aureus CIO613, Staphylococcus epidermidis CIO615, and Escherichia coli CIO465. Methods: This experimental study was carried out through the Mueller-Hinton agar dilution method. 43 to 3 µM melatonin concentrations were analyzed on a 0.5 McFarland adjusted suspension of each strain. Finally a 1 μl of each microorganism was spread on the agar and incubated at 37 °C for 24 and 48 h. Results: Melatonin showed an antibacterial effect against the four bacteria studied with a 43 µM concentration at 24 and 48 h. Conclusions: Melatonin has excellent antimicrobial activity against Streptococcus mutans CIO315, Staphylococcus aureus CIO613, Staphylococcus epidermidis CIO615, and Escherichia coli CIO465 at a concentration of 43 µM, indicating that it could be an option in the prevention and treatment of oral diseases such as dental caries and periodontitis.

The actions made by health institutions in the prevention and control of dental caries have not been enough to achieve an important reduction of this disease. At the present moment, the microbiological control or replacement therapy applied for the prevention of the infectious diseases is just a hypothetical possibility. However, it is important to study and analyze the real value that this strategie can have in the future as a way to control dental problems, specifically dental caries. This therapeutical possibility acquires more importance with the awareness that preventive measures taken at the present time don’t have the expected impact. The goal of this article is to present an analysis of the researches made in  the search, improvement and  application of Streptococcus mutans  strains in the microbiological  control on S. mutans native strains and thus, the prevention of dental  caries. In the history of the studies made in microbiological control, the  works made by Hillman et al with of S. mutans mutant strains, JH1001, JH1005, JH1140 and BCS3-L1 were distinguished. In this group of  strains, the genetic stability and also the capacity to colonize and stay  on the oral cavity and other important characteristics of its use on microbiological control were evaluated. The  advances obtained in these works in conjunction with the availability of more efficient techniques of  genetic engineering allow to think that the achievement of the perfect strain for prevention of dental caries is closer.

Dental caries is a localized, transmissible, pathological infectious process that ends up in the destruction of hard dental tissue. Streptococcus mutans is considered to be the main cause of dental caries. Indeed, numerous reports have shown the close relationship between salivary levels of S. mutans and dental caries. The purpose of this study was to determine the relationship between the presence of Streptococcus mutans and dental caries, and to evaluate the antimicrobial susceptibility of the isolates. Unstimulated saliva was collected from 53 3 to 5-year-old children from the Diego Torres school in Turmequé (Boyacá,Colombia). Saliva samples were vortexed and serially diluted in 0.05 M phosphate buffer. Aliquots of 100ul of the appropriate dilutions were cultured on Mitis Salivarius Bacitracin agar medium for the selective isolation of S. mutans, and incubated anaerobically for two days at 37o C. The minimal inhibitory concentrations of the S. mutans isolates were evaluated against penicillin, amoxicillin, cefazolin, erythromycin, clindamycin, imipenem and vancomycin by an agar dilution method. The dental caries experience in these children was 66% (35/53) and S. mutans was found in the saliva of 33 children (62%);21 of them had dental caries and 12 did not. In the 20 children from whom S. mutans was not isolated, 14(70%) were found to have caries. There were no statistically significant differences in S. mutans counts between the group with dental caries and the caries-free group (p=0.21). All isolates were highly sensitive to penicillin, amoxycillin, cefazolin, erythromycin, clindamycin, imipenem and vancomycin; 50 and90% of the strains from S. mutans were inhibited by concentrations of less than 0.12 and 0.5 ug/ml, respectively, for all antibiotics studied. In conclusion, not all of the children hosting this microorganism had caries, and the S. mutans strains were highly sensitive to the antibiotics tested.