Abstract
Synergistic interactions between natural bioactive compounds from medicinal plants and antibiotics may exhibit therapeutic benefits, acting against oral cariogenic and opportunistic pathogens. The aim of the presented work was to assess the antibacterial activity of berberine chloride (BECl) in light of the effect exerted by common antibiotics on selected reference strains of oral streptococci (OST), and to evaluate the magnitude of interactions. Three representative oral microorganisms were investigated: Streptococcus mutans ATCC 25175 (SM), S. sanguinis ATCC 10556 (SS), S. oralis ATCC 9811 (SO) and microdilution tests, along with disc diffusion assays were applied. Here, we report that growth (viability) of all oral streptococci was reduced by exposure to BECl and was dependent primarily on exposure/incubation time. A minimum inhibitory concentrations (MIC) of BECl against OST ranged from 512 µg/mL (SS) to 1024 µg/mL (SM, SO). The most noticeable antibacterial effects were observed for S. sanguinis (MIC 512 µg/mL) and the most significant synergistic action was found for the combinations BECl-penicillin, BECl-clindamycin and BECl-erythromycin. The S. oralis reflects the highest MBC value as assessed by the AlamarBlue assay (2058 µg/mL). The synergy between berberine and common antibiotics demonstrates its potential use as a novel antibacterial tool for opportunistic infections and also provides a rational basis for the use of berberine as an oral hygiene measure.
Highlights
The highly diverse oral microbiota and their individual composition, including variable oral biofilms and pathogenicity, has an impact on the health and disease status of the host [1,2]
Our study was designed to determine the antibacterial effect of berberine chloride (BECl) and to evaluate for the first time, whether the addition of other antibiotics may augment the biological effect of this natural substance
The minimum inhibitory concentrations (MIC) values obtained for each species may not represent the concentration that inhibits biofilm formation, which are more resilient than planktonic forms
Summary
The highly diverse oral microbiota and their individual composition, including variable oral biofilms and pathogenicity, has an impact on the health and disease status of the host [1,2]. Molecular techniques have estimated the diversity within the oral cavity to consist of over 700 species or phenotypes/. It is estimated that twenty-five non-homogeneous species of oral streptococci inhabit the human oral cavity and represent about 20% of the total oral bacteria [4]. The relative pathogenicity of certain oral microbial species such as the mutans streptococci group (Streptococcus mutans, S. mittis, S. sobrinus) is undoubtfully associated with their ability to form biofilms, which are resistant to mechanical stress or antibiotic treatment [6]. Biofilm bacteria have been indicated to be up to 1000-fold more tolerant of antibiotics, and this makes it hard to treat oral streptococci with standard antimicrobials
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