The present study evaluated the antimicrobial activity of three root canal irrigants against Enterococcus faecalis, Candida albicans, and Staphylococcus aureus. These microorganisms were incubated in the presence of citric acid (6 and 10%), EDTA (17%), and NaOCl (0.5, 1.0, 2.5, and 5.25%). Agar diffusion tests were performed and redox indicator resazurin was used to evaluate the inhibitory effect of the irrigants on the metabolic activity of these microorganisms. The mean diameters of the inhibition zones for the C. albicans cultures were 11.6 mm (17% EDTA), 5.5 mm (0.5% NaOCl), 12.9 mm (1% NaOCl), 22.1 mm (2.5% NaOCl), and 28.5 mm (5.25% NaOCl). The mean diameters of the inhibition zones for E. faecalis were 2.8 mm (1% NaOCl), 5.4 mm (2.5% NaOCl), and 8.3 mm (5.25% NaOCl). For S. aureus, the mean values were 8.0 mm (17% EDTA), 3.0 mm (1% NaOCl), 8.8 mm (2.5% NaOCl), and 10.0 mm (5.25% NaOCl). Most of the irrigant solutions presented effective antimicrobial activity against C. albicans. A high inhibitory effect on the metabolic activity of E. faecalis was detected when the microorganisms were incubated with 17% EDTA. The same result was reached when S. aureus was incubated in the presence of > 2.5% NaOCl. Altogether, these results indicate that 2.5% and 5.25% NaOCl are microbicides against S. aureus while 0.5% and 1% NaOCl are only microbiostatic against the tested bacteria. The 6% and 10% citric acid as well as 17% EDTA did not affect the viability of any of the assayed microorganisms.

We investigated the effect of two modulators of protein kinase C, sphingosine and phorbol-12-myristate-13-acetate (PMA), on the growth and dimethylsulfoxide (DMSO)-induced differentiation in Herpetomonas samuelpessoai. Sphingosine did not stimulate the transformation of undifferentiated-promastigotes in differentiated-paramastigotes. PMA alone or in association with DMSO increased the number of paramastigotes in comparison to control cells. DMSO inhibited the parasite growth (35%) and several unusual morphological features resembling aberrant cell division were observed. Sphingosine did not significantly reduce the growth in contrast to PMA. Collectively, our results demonstrated that the reduction of the proliferation translates in an increase of the differentiation rate in the insect trypanosomatid H. samuelpessoai.