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Abstract
Escherichia coli O157:H7 is one of the most important pathogens worldwide. In this study, three different kinds of enzymes, DNase I, proteinase K and cellulase were evaluated for inhibitory or degrading activity against E. coli O157:H7 biofilm by targeting extracellular DNA, proteins, and cellulose, respectively. The cell number of biofilms formed under proteinase K resulted in a 2.43 log CFU/cm2 reduction with an additional synergistic 3.72 log CFU/cm2 reduction after NaClO post-treatment, while no significant reduction occurred with NaClO treatment alone. It suggests that protein degradation could be a good way to control the biofilm effectively. In preformed biofilms, all enzymes showed a significant reduction of 16.4–36.7% in biofilm matrix in 10-fold diluted media (p < 0.05). The sequential treatment with proteinase K, cellulase, and NaClO showed a significantly higher synergistic inactivation of 2.83 log CFU/cm2 compared to 1.58 log CFU/cm2 in the sequence of cellulase, proteinase K, and NaClO (p < 0.05). It suggests that the sequence of multiple enzymes can make a significant difference in the susceptibility of biofilms to NaClO. This study indicates that the combination of extracellular polymeric substance-degrading enzymes with NaClO could be useful for the efficient control of E. coli O157:H7 biofilms.
Highlights
Escherichia coli O157:H7 is one of the most important foodborne pathogens worldwide, causing gastroenteritis, hemolytic uremic syndrome (HUS), hemorrhagic colitis and thrombotic thrombocytopenic purpura in susceptible groups such as children and elderly people[1]
When the inoculum was incubated in the presence of deoxyribonuclease I (DNase I), no reduction in biofilm formation occurred compared to the absence of DNase I, regardless of the nutrient concentrations
Methods using extracellular polymeric substances (EPS)-degrading enzymes have been studied for potential applications in biofilm control[25]
Summary
Escherichia coli O157:H7 is one of the most important foodborne pathogens worldwide, causing gastroenteritis, hemolytic uremic syndrome (HUS), hemorrhagic colitis and thrombotic thrombocytopenic purpura in susceptible groups such as children and elderly people[1] It is generally highly associated with cattle, and contaminated fresh produce has been recently implicated in foodborne illness by E. coli O157:H72. Bacterial cells adhere to abiotic surfaces and produce film-like structures that protect the cells from environmental stresses, such as disinfection in a food processing environment[6,7,8,9,10,11] This structure, called biofilm, can lead to serious problems during food production, distribution and consumption by cross-contamination[6,12,13,14,15,16]. Kim et al (2013) applied proteinase K, trypsin, subtilisin and dispersin B to biofilms formed on a fouled reverse osmosis membrane, and showed different efficiencies of these enzymes[25]
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