Article

Effects of sub-minimum inhibitory concentrations of antimicrobial agents on Streptococcus mutans biofilm formation.

Department of Operative Dentistry & Endodontics, School of Stomatology, Fourth Military Medical University, 145 Changle West Road, Xi'an 710032, Shaanxi, China.
International journal of antimicrobial agents (Impact Factor: 3.03). 03/2012; 39(5):390-5. DOI: 10.1016/j.ijantimicag.2012.01.009
Source: PubMed

ABSTRACT Many studies have demonstrated that sub-minimum inhibitory concentrations (sub-MICs) of antimicrobial agents can inhibit bacterial biofilm formation. However, the mechanisms by which antimicrobial agents at sub-MICs inhibit biofilm formation remain unclear. At present, most studies are focused on Gram-negative bacteria; however, the effects of sub-MICs of antimicrobial agents on Gram-positive bacteria may be more complex. Streptococcus mutans is a major cariogenic bacterium. In this study, the S. mutans growth curve as well as the expression of genes related to S. mutans biofilm formation were evaluated following treatment with 0.5× MIC of chlorhexidine (CHX), tea polyphenols and sodium fluoride (NaF), which are common anticaries agents. The BioFlux system was employed to generate a biofilm under a controlled flow. Morphological changes of the S. mutans biofilm were observed and analysed using field emission scanning electron microscopy and confocal laser scanning microscopy. The results indicated that these three common anticaries agents could significantly upregulate expression of the genes related to S. mutans biofilm formation, and S. mutans exhibited a dense biofilm with an extensive extracellular matrix following treatment with sub-MICs of NaF and CHX. These findings suggest that sub-MICs of anticaries agents favour S. mutans biofilm formation, which might encourage dental caries progression.

0 Bookmarks
 · 
179 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since Streptococcus mutans is the principal etiologic agent causing dental caries, by encompassing an array of unique virulence traits, emerging treatment strategies that specifically target the virulence of this pathogen may be promising as alternative approaches compared to conventional antibiotic therapy. In this perspective, we investigated chloroform extract of cell-free culture supernatant from mangrove rhizosphere bacterium Bacillus amyloliquefaciens (MMS-50) in terms of anticariogenic properties of S. mutans, without suppressing its viability. Crude chloroform extract of MMS-50 was subjected to column and high performance liquid chromatographic techniques to obtain the active fraction (AF), and MMS-50 AF was used for all further assays. GC–MS and FT-IR were carried out to identify the major components present in MMS-50 AF. Comparative gene expression analysis of some biofilm-forming and virulence genes (vicR, comDE, gtfC, and gbpB) was done by real-time PCR. Cyclo(L-leucyl-L-prolyl) was found to be the chief compound in MMS-50 AF responsible for bioactivity. The minimum and maximum inhibitory concentrations of MMS-50 AF against S. mutans were found to be 100 and 250 μg/mL, respectively. Anti-virulence assays performed using below-sub-MIC levels of MMS-50 AF (30 μg/mL) resulted in significant reduction in adherence (68%), acid production, acid tolerance, glucan synthesis (32%), biofilm formation (53.5%) and cell surface hydrophobicity, all devoid of affecting its viability. The micrographs of CLSM and SEM further confirmed the antibiofilm and anti-virulence efficacies of MMS-50 AF. Expression data showed significant reduction in expression of all studied virulence genes. Thus, the current study unveils the anticariogenic potential of cyclo(L-leucyl-L-prolyl) from B. amyloliquefaciens, as well as its suitability as a novel and alternative anticariogenic agent against dental caries.
    Research in Microbiology 01/2014; · 2.89 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Triclosan is a general membrane-active agent with a broad-spectrum antimicrobial activity that is commonly used in oral care products. In this study, we investigated the effect of sub-minimum inhibitory concentrations (MICs) of triclosan on the capacity of the cariogenic bacterium Streptococcus mutans to form biofilm and adhere to oral epithelial cells. As quantified by crystal violet staining, biofilm formation by two reference strains of S. mutans was dose-dependently promoted, in the range of 2.2- to 6.2-fold, by 1/2 and 1/4 MIC of triclosan. Observations by scanning electron microscopy revealed the presence of a dense biofilm attached to the polystyrene surface. Growth of S. mutans in the presence of triclosan at sub-MICs also increased its capacity to adhere to a monolayer of gingival epithelial cells. The expression of several genes involved in adherence and biofilm formation in S. mutans was investigated by quantitative RT-PCR. It was found that sub-MICs of triclosan significantly increased the expression of comD, gtfC, and luxS, and to a lesser extent of gtfB and atlA genes. These findings stress the importance of maintaining effective bactericidal concentrations of therapeutic triclosan since sub-MICs may promote colonization of the oral cavity by S. mutans.
    PLoS ONE 01/2014; 9(2):e89059. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Citrobacter sp. is a cause of significant opportunistic nosocomial infection and frequently found in human and animal feces, soil and sewage water and even industrial waste or putrefaction. Biofilm formation is an important virulence trait of Citrobacter sp. pathogens but the process and characteristics of this formation were unclear. Therefore, we have been employing in vitro assays to study nutritional and environmental parameters which might influence biofilm formation of Citrobacter werkmanii BF-6 using the 96-well microtiter plates. Meanwhile, the relative transcript levels of biofilm formation genes were also detected by RT-PCR. Our results indicated that the capacity of Citrobacter werkmanii BF-6 to form biofilms could be affected by culture temperature, media, time, pH and osmotic agents including glucose, sucrose, NaCl, and KCl. Meanwhile, confocal laser scanning microscopy (CLSM) results illustrated that the structure of biofilms and extracellular polysaccharide (EPS) would be influenced by 100 mM NaCl or 100 mM KCl. In addition, nine biofilm formation genes (bsmA, bssR, bssS, csgD, csgE, csgF, mrkA, mrkB, and mrkE) contributed to planktonic and biofilm growth. Our data suggest that the biofilm formation of C. werkmanii BF-6 could be affected by nutritional and environmental factors which would pave a way to prevent and eliminate the biofilm formation with proper strategies.
    Journal of Microbiology and Biotechnology 09/2013; · 1.40 Impact Factor

Full-text

View
9 Downloads
Available from
Jun 20, 2014