Antimicrobial nisin acts against saliva derived multi-species biofilms without cytotoxicity to human oral cells

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.

Biomedical applications of nisin

“…Shin et al . () also reported that nisin exerted anti‐biofilm effects on saliva derived multispecies biofilms without causing cytotoxicity to human oral cells (Fig. ).…”

“…; Shin et al . ). Similar to other lantibiotics, nisin contains several unusual amino acids as a result of enzymatic post‐translational modifications (Sahl et al .…”

“…; Shin et al . ). Studies have demonstrated that purified nisin and nisin in combination with other antibiotics can be effective against Gram‐negative pathogens and that certain bioengineered nisin variants can enhance the activity against both Gram‐positive and Gram‐negative pathogens (Kuwano et al .…”

“…In addition, Shin et al . () demonstrated that high‐purity nisin Z can inhibit the growth of Gram‐negative oral colonizing pathogens, including Porphyromonas gingivalis , Prevotella intermedia , Aggregatibacter actinomycetemcomitans and Treponema denticola . Shin et al .…”

Probiotics, including nisin‐based probiotics, improve clinical and microbial outcomes relevant to oral and systemic diseases

“…However, more detailed microbial studies are needed to measure the specific alterations in the oral microbiome before and after nisin use, since it is important to maintain oral commensal bacteria while selectively removing the pathogenic microbes. Recently, 2 studies examined the effects of a highly purified form of nisin on oral salivary‐derived biofilms and planktonic forms of oral gram‐positive and gram‐negative oral bacteria, including Porphyromonas gingivalis , Prevotella intermedia , A. actinomycetemcomytans , Treponema denticola , and Enterococcus faecalis . Nisin inhibited the planktonic growth of these pathogenic bacteria significantly at concentrations ranging from 2.5 to 50 μg/ml, and the inhibitory effects increased with increasing concentrations of nisin up to 200 μg/ml.…”