Low concentrations of honey reduce biofilm formation, quorum sensing, and virulence in Escherichia coli O157:H7

School of Chemical Engineering, Yeungnam University, Gyeongsan, 712-74, Republic of Korea.
Biofouling (Impact Factor: 3.42). 11/2011; 27(10):1095-104. DOI: 10.1080/08927014.2011.633704
Source: PubMed


Bacterial biofilms are associated with persistent infections due to their high resistance to antimicrobial agents. Hence, controlling pathogenic biofilm formation is important in bacteria-related diseases. Honey, at a low concentration of 0.5% (v/v), significantly reduced biofilm formation in enterohemorrhagic Escherichia coli O157:H7 without inhibiting the growth of planktonic cells. Conversely, this concentration did not inhibit commensal E. coli K-12 biofilm formation. Transcriptome analyses showed that honey significantly repressed curli genes (csgBAC), quorum sensing genes (AI-2 importer and indole biosynthesis), and virulence genes (LEE genes). Glucose and fructose in the honeys were found to be key components in reducing biofilm formation by E. coli O157:H7 through the suppression of curli production and AI-2 import. Furthermore, honey, glucose and fructose decreased the colonization of E. coli O157:H7 cells on human HT-29 epithelial cells. These results suggest that low concentrations of honey, such as in honeyed water, can be a practical means for reducing the colonization and virulence of pathogenic E. coli O157:H7.

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    • "This effect of honey is mainly associated with low (<10 kDa) molecular weight (MW) components and MRJP1. In addition, glucose and fructose have been recently identified as major components of honey responsible for biofilm reduction in pathogenic Escherichia coli (Lee et al., 2011). Taken together, monosaccharides and MRJP1, which are found in every natural honey, could take part in inhibition of wound biofilm formation. "
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    ABSTRACT: Biofilm growth and its persistence within wounds have recently been suggested as contributing factors to impaired healing. The goal of this study was to investigate the anti-biofilm effects of several honey samples of different botanical origin, including manuka honey against Proteus mirabilis and Enterobacter cloacae wound isolates. Quantification of biofilm formation was carried out using a microtiter plate assay. All honeys at a sub-inhibitory concentration of 10% (w/v) significantly reduced the biofilm development of both isolates. Similarly, at a concentration of 50% (w/v), each of the honeys caused significant partial detachment of Pr. mirabilis biofilm after 24 h. On the other hand, no honey was able to significantly detach Ent. cloacae biofilm. In addition, treatment of Ent. cloacae and Pr. mirabilis biofilms with all honeys resulted in a significant decrease in colony-forming units per well values in a range of 0.35-1.16 and 1.2-7.5 log units, respectively. Of the tested honeys, manuka honey possessed the most potent anti-biofilm properties. Furthermore, methylglyoxal, an antibacterial compound of manuka honey, was shown to be responsible for killing biofilm-embedded wound bacteria. These findings suggest that manuka honey could be used as a potential therapy for the treatment of wounds containing Pr. mirabilis or Ent. cloacae. Copyright © 2013 John Wiley & Sons, Ltd.
    Phytotherapy Research 01/2014; 28(1):69-75. DOI:10.1002/ptr.4957 · 2.66 Impact Factor
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    • "Therefore, the cellular processes of biofilm formation, maintenance, and dispersal are important targets for the discovery of new inhibitors (Landini et al. 2010). One of these approaches involves the use of compounds that interrupt bacterial communication in biofilms , instead of simply killing the bacteria (Kaufmann et al. 2008; Lee et al. 2011; Jakobsen et al. 2012). "
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    ABSTRACT: Quorum sensing (QS) is an important regulatory mechanism in biofilm formation and differentiation. Interference with QS can affect biofilm development and antimicrobial susceptibility. This study evaluates the potential of selected phytochemical products to inhibit QS. Three isothiocyanates (allylisothiocyanate - AITC, benzylisothiocyanate - BITC and 2-phenylethylisothiocyanate - PEITC) and six phenolic products (gallic acid - GA, ferulic acid - FA, caffeic acid - CA, phloridzin - PHL, (-) epicatechin - EPI and oleuropein glucoside - OG) were tested. A disc diffusion assay based on pigment inhibition in Chromobacterium violaceum CV12472 was performed. In addition, the mechanisms of QS inhibition (QSI) based on the modulation of N-acyl homoserine lactone (AHLs) activity and synthesis by the phytochemicals were investigated. The cytotoxicity of each product was tested on a cell line of mouse lung fibroblasts. AITC, BITC and PEITC demonstrated a capacity for QSI by modulation of AHL activity and synthesis, interfering the with QS systems of C. violaceum CviI/CviR homologs of LuxI/LuxR systems. The cytotoxic assays demonstrated low effects on the metabolic viability of the fibroblast cell line only for FA, PHL and EPI.
    Biofouling 12/2013; DOI:10.1080/08927014.2013.852542 · 3.42 Impact Factor
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    • "Additionally, microtiter plates allow " multiplexing " , i.e., multiple organisms and/or treatments can be included in a single run (Coenye and Nelis, 2010), and several well established protocols are available for determination of macroscale parameters related to the biofilm (Table 1). Microtiter plates have been extensively used for biofilm studies addressing microbial adhesion (Moreira et al., 2013a; Simões et al., 2010), biofilm inhibition (Cady et al., 2012; Lee et al., 2011) and screening of antimicrobial compounds Journal of Microbiological Methods 95 (2013) 342–349 ⁎ Corresponding author at: Department of Chemical Engineering, Faculty of Engineering University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal. Tel.: +351 225081668; fax: +351 5081449. "
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    ABSTRACT: Microtiter plates with 96 wells have become one of the preferred platforms for biofilm studies mainly because they enable high-throughput assays. In this work, macroscale and microscale methods were used to study the impact of hydrodynamic conditions on the physiology and location of Escherichia coli JM109(DE3) biofilms formed in microtiter plates. Biofilms were formed in shaking and static conditions, and two macroscale parameters were assayed: the total amount of biofilm was measured by the crystal violet assay and the metabolic activity was determined by the resazurin assay. From the macroscale point of view, there were no statistically significant differences between the biofilms formed in static and shaking conditions. However, at a microscale level, the differences between both conditions were revealed using scanning electron microscopy (SEM). It was observed that biofilm morphology and spatial distribution along the wall were different in these conditions. Simulation of the hydrodynamic conditions inside the wells at a microscale was performed by computational fluid dynamics (CFD). These simulations showed that the shear strain rate was unevenly distributed on the walls during shaking conditions and that regions of higher shear strain rate were obtained closer to the air/liquid interface. Additionally, it was shown that wall regions subjected to higher shear strain rates were associated with the formation of biofilms containing cells of smaller size. Conversely, regions with lower shear strain rate were prone to have a more uniform spatial distribution of adhered cells of larger size. The results presented on this work highlight the wealth of information that may be gathered by complementing macroscale approaches with a microscale analysis of the experiments.
    Journal of Microbiological Methods 10/2013; 95:342-349. DOI:10.1016/j.mimet.2013.10.002 · 2.03 Impact Factor
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