TITLE:
Influence of Sub-Lethal and Lethal Concentrations of Chlorhexidine on Morphology and Glucosyltransferase Genes Expression in Streptococcus mutans UA159
AUTHORS:
Andréa Cristina Barbosa da Silva, Rafael Nóbrega Stipp, Renata de Oliveira Mattos-Graner, Fábio Correia Sampaio, Demetrius Antônio Machado de Araújo
KEYWORDS:
Planktonic Cells, Biofilm, Microorganism, Scanning Electron Microscopy
JOURNAL NAME:
Advances in Microbiology,
Vol.4 No.13,
October
21,
2014
ABSTRACT: Chlorhexidine
(CHX) is regarded as one of the most successful antiplaque agents in controlling
the formation of dental biofilm. Nevertheless, molecular mechanisms of their
effects in Streptococcus mutans are
largely unknown. In this work, the effects of sub-lethal and lethal
concentrations of chlorhexidine (CHX) on planktonic or biofilm-organized Streptococcus mutans cells were
investigated in dose- and time-dependent manner. The Minimum Inhibitory Concentration
(MIC) and the Minimum Bactericidal Concentration (MBC) for planktonic cells and
biofilm conditions were determined by standard methods. Quantitative PCR (qPCR)
was used to quantify the relative levels of glucosyltransferase
B (gtfB), gtfC and gtfD transcription
of S. mutans in the presence of CHX.
The CHX activity in the initial biofilm structure and morphological alterations
in planktonic cells were examined by Scanning Electron Microscopy (SEM). The
results indicate that CHX increased expression of gtfC and gtfD in
planktonic S. mutans cells and CHX
reduced the expression of gtfB, gtfC, and gtfD in biofilms. High concentrations of CHX resulted in several
wilted S. mutans planktonic cells
with spilled intracellular material, while decreased cells’ chain length and
matrix was found when the initial biofilm was exposed to increasing
concentrations of CHX. CHX’s effects against bacteria depend on the type of growth organization and the concentration
and time of exposure to the drug. At sub-lethal concentrations, CHX affects the
expression of glucosyltransferases, which may have anticariogenic effect.