Correlation Analyses of the Oral Biofilm Growth Inhibition towards Hydrophobicity Reduction of Oral Pathogenic Bacteria

Bacteria have a tendency to form multicellular biofilms, which adhere to surfaces and contain extracellular polymeric substances (EPS). This tendency is accompanied by hydrophobic interactions, which are vital in the biofilm attachment process. Oral biofilms contribute to a range of oral health issues, including gingivitis, dental caries, and halitosis. Therefore, this research aimed to investigate the correlation between oral biofilm growth inhibition and hydrophobicity reduction in Streptococcus mutants, Streptococcus sanguinis, Lactobacillus acidophilus, and Actinomyces viscosus. Essential oil-derived compounds, namely eugenol, C-10 massoia lactone, thymol, cinnamaldehyde, and zerumbone, were applied in the experiment. A microdilution assay using crystal violet staining evaluated the oral microbes' biofilm growth. The adhesion of microbes to hexadecane was measured to assess hydrophobicity reduction, which was analyzed correlatively using PAST (Paleontological Statistics) software and the Principal Component Analysis (PCA) method. The results showed a positive correlation of the hydrophobicity reduction towards the biofilm formation inhibition for all tested microbes (graphical angle <45°). The Principal Component (PC) analysis, based on the eigene values, showed that PC1 and PC2 accounted for 54.149% and 25.652% of the total variation, respectively. These two components explained 79.801% of the total variation, indicating a significant level of variability. This finding supported the notion that a greater reduction in microbial hydrophobicity was associated with stronger inhibitory activity against planktonic growth. The hydrophobicity reduction assay may indicate a potential of bioactive compounds against biofilm growth inhibition of oral microbes.