Abstract
Objectives: Nisin is a lantibiotic widely used for the preservation of food and beverages. Recently, investigators have reported that nisin may have clinical applications for treating bacterial infections. The aim of this study was to investigate the effects of ultra pure food grade Nisin ZP (>95% purity) on taxonomically diverse bacteria common to the human oral cavity and saliva derived multi-species oral biofilms, and to discern the toxicity of nisin against human cells relevant to the oral cavity.Methods: The minimum inhibitory concentrations and minimum bactericidal concentrations of taxonomically distinct oral bacteria were determined using agar and broth dilution methods. To assess the effects of nisin on biofilms, two model systems were utilized: a static and a controlled flow microfluidic system. Biofilms were inoculated with pooled human saliva and fed filter-sterilized saliva for 20–22 h at 37°C. Nisin effects on cellular apoptosis and proliferation were evaluated using acridine orange/ethidium bromide fluorescent nuclear staining and lactate dehydrogenase activity assays.Results: Nisin inhibited planktonic growth of oral bacteria at low concentrations (2.5–50 μg/ml). Nisin also retarded development of multi-species biofilms at concentrations ≥1 μg/ml. Specifically, under biofilm model conditions, nisin interfered with biofilm development and reduced biofilm biomass and thickness in a dose-dependent manner. The treatment of pre-formed biofilms with nisin resulted in dose- and time-dependent disruption of the biofilm architecture along with decreased bacterial viability. Human cells relevant to the oral cavity were unaffected by the treatment of nisin at anti-biofilm concentrations and showed no signs of apoptotic changes unless treated with much higher concentrations (>200 μg/ml).Conclusion: This work highlights the potential therapeutic value of high purity food grade nisin to inhibit the growth of oral bacteria and the development of biofilms relevant to oral diseases.
Highlights
Dental plaque is an architecturally complex bacterial multispecies biofilm community (Marsh, 2010; Zijnge et al, 2010)
University of Michigan, School of Dentistry, Ann Arbor, MI, USA), Streptococcus mutans ATCC 25175, and Aggregatibacter actinomycetemcomitans Y4 were grown on Brain Heart Infusion agar (BHI, Difco, Sparks, MD, USA) and cultured in BHI broth media
S. mutans, a cariogenic Gram-positive bacteria, showed a 1.5- to 3-fold higher sensitivity to nisin when compared to the two commensal organisms S. gordonii and S. oralis (Figure 1; Table 1)
Summary
Dental plaque is an architecturally complex bacterial multispecies biofilm community (Marsh, 2010; Zijnge et al, 2010). In part, for the accumulation of pathogens that are associated with dental caries, periodontal disease, and pulpal infections (Marsh, 2003). Strategies to control biofilms and their contained species have met with difficulties, as is evidenced by the public health burden associated with poor oral health. Given the public health burden associated with dental plaque, new candidate anti-biofilm technologies are currently being investigated. These include modifications to traditional approaches, such as the development of improved antimicrobial compounds and formulations (zinc, cetylpyridinium chloride, stannous compounds, natural agents) (Allaker and Douglas, 2009; Marsh, 2010) to more innovative technologies, such as those that display antimicrobial and anti-biofilm effects (Kaplan, 2010). One technology that has recently garnered attention is the use of bacteriocins, such as nisin, which is produced by Lactococcus lactis (Pepperney and Chikindas, 2011; Arthur et al, 2014)
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