Starvation Survival and Biofilm Formation under Subminimum Inhibitory Concentration of QAMs

Abstract

Quaternary ammonium methacrylates (QAMs) are useful antimicrobial compounds against oral bacteria. Here, we investigated the effects of two QAMs, dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM), on biofilm formation, survival and development of tolerance by biofilm, and survival and development of tolerance against QAMs after prolonged starvation. Enterococcus faecalis (E. faecalis), Streptococcus gordonii (S. gordonii), Lactobacillus acidophilus (L. acidophilus), and Actinomyces naeslundii (A. naeslundii) were used. Minimum inhibitory concentration (MIC) of QAMs against multispecies biofilm was determined. Biofilm formed under sub-MIC was observed by crystal violet staining and confocal laser scanning microscopy (CLSM). Metabolic activity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactic acid production measurement. Development of tolerance was determined by MIC values before and after exposure to QAMs or after prolonged starvation. It was found that E. faecalis and S. gordonii could survive and form biofilm under sub-MIC of QAMs. Lactic acid production from biofilms formed under sub-MIC was significantly higher than control specimens ( p < 0.05 ). The exposure to sub-MIC of QAMs promoted biofilm formation, and prolonged starvation or prolonged contact with sub-MIC helped bacteria develop tolerance against killing by QAMs.

Influence of Needle Design and Irrigant Flow Rate on the Removal of Enterococcus faecalis Biofilms In Vitro

“…After two weeks in culture, bacterial biofilms remained viable as shown by the high percentage (approx. 75%) of living bacteria (SYTO 9 positive) in control specimens; such stable measurements are in line with previously published data from Tiwari et al [24] and were expected from the experimental set-up used in this study. Double-stained bacteria (SYTO 9/PI positive), so-called "damaged cells", were considered as dead bacteria because double-positive bacteria were previously shown to lose their ability to grow on agar plates.…”

Biofilm Production and Porin Permeability Activity in Clinical Isolates of Ciprofloxacin-Resistant Klebsiella pneumoniae in the Tertiary Hospital in Purwokerto, Indonesia

“…This value is lower than the control, which is 10.15×10 7 CFU/mL. Tiwari et al [61] used quaternary ammonium methacrylate as an antimicrobial compound, resulting in resistant isolates. The results showed that biofilm formation below the MIC value would be significantly thinner, indicating its formation was inhibited by antimicrobial compounds.…”

“…Antibiotic susceptibility can be affected by changes in the biofilm matrix. Exopolysaccharides (EPS) influence material diffusion into and out of the biofilm, thereby creating microenvironmental diversity in the biofilm [61]. Microdilution analysis is used to determine the volume of living cells in biofilm below the MIC value.…”

Silica nanoparticles containing nano-silver and chlorhexidine to suppress Porphyromonas gingivalis biofilm and modulate multispecies biofilms toward healthy tendency

“…MIC is the minimum concentration of an antimicrobial agent to completely inhibit bacteria growth. The MIC of nMS-nAg-Chx against P. gingivalis biofilm was determined by a two-fold serial dilution method on a 96-well plate [ 48 ]. nMS-nAg-Chx was dispersed in sterile distilled water and diluted with a BHI solution to prepare the starting concentrations (150 µg/mL).…”