The Effect of Benzyl Isothiocyanate On The Expression of Genes Encoding NADH Oxidase And Fibronectin-Binding Protein In Oral Streptococcal Biofilms

Abstract

Background: Recent studies have shown that antibiotic treatment results in up- or down regulation of several virulence-associated genes. The genes encoding NADH oxidase (nox) and fibronectin-binding protein (fbp) are known to play important roles in biofilms of some oral bacterial species. The objective was to study the effect of benzyl isothiocyanate (BITC), an antimicrobial agent from Miswak plant, on the expression of nox and fbp genes in some oral streptococci.Methods: Bacterial strains were grown as biofilms in brucella broth. The crystal violet stained biofilms were quantified by optical density measurements at 590 nm. The biofilms were treated with an antimicrobial agent (BITC) for 2 h and fold change in mRNA expression of nox and fbp genes in BITC treated selected oral streptococci was measured by comparative ∆∆Ct method on Real-Time PCR machine.Results: The highest amount of biofilm mass was produced by A. defectiva, followed by S. gordonii, S. mutans, G. elegans and G. adiacens. Upon treatment with BITC, S. gordonii biofilms showed highest mRNA expression for both fbp and nox genes. Mean (SE) folds increase in the expression of nox mRNA: S. gordonii 2 (0.30), followed by S. mutans 1.25 (0.18), A. defectiva 1.03 (0.09), G. adiacens 0.7 (0.03). Similarly for fbp, folds increase in mRNA expression was: S. gordonii 2.65 (0.03), followed by A. defectiva 2.09 (0.60), G. elegans 1.61 (0.40), S. mutans 1.57 (0.20), and G. adiacens 0.58 (0.06). G. elegans mRNA levels for nox were extremely low (0.006-fold). Conclusion: BITC treatment of the biofilms caused an upregulation of biofilm-associated genes fbp and nox genes in most of the tested species suggesting the significance of these genes in biofilm lifestyle of these oral bacteria. Increased expression of nox and fbp genes in the biofilm lifestyle of these species needs further investigation to understand if it contributes to antimicrobial resistance.