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Antimicrobial Photodynamic Treatment for Surface Sanitation


Certain non-toxic dyes (photosensitizers), when illuminated with visible light, can produce short-lived cytotoxic species that possess antimicrobial activity. The term Antimicrobial Photodynamic Treatment (APDT) has been adopted to describe this process. Our preliminary results show that APDT is effective against such important food-borne pathogens as Escherichia coli O157:H7 and Listeria monocytogenes, and, recently, we have shown that APDT can also be successfully applied for inactivation of microorganisms present in biofilms. These features make APDT a promising approach to be explored for the disinfection of food contact surfaces.
Another feature which makes APDT an appealing technology is that development of resistance to APDT has not been reported, which is not the case with commonly used sanitizers. In addition, sanitizers currently used by the food industry very often are not effective against bacterial spores, biofilms, or viruses. This increases the need to develop novel cost-effective strategies for surface decontamination and sanitation that will decrease bacterial loads of ready-to-eat foods, improve shelf-life, decrease possible economic losses due to spoilage and recalls, and, ultimately minimize the risk of infections.
Although clinical applications of APDT, including combating infections in wounds and burns, infections in body cavities (such as the mouth, ear, sinus, and stomach) and surface infections of cornea and skin, are being investigated, the efficacy of this method for surface disinfection has not been investigated. This project's research aims at assessing the effectiveness of a wide range of photosensitizers, including those described to be effective in clinical studies as well as new ones, for decontamination of surfaces composed of different materials relevant to the agri-food industry such as plastics, stainless steel, etc. The efficacy of the treatment will be optimized in terms of photosensitizer concentration, time of treatment and intensity of light necessary to initiate an effect. The possibility of creating self-decontaminating surfaces by incorporation of the chosen photosensitizer into suitable materials will be explored.
The objective of this investigation will be the development of new surface sanitation techniques for use in the agri-food industry. This can lead directly to improvement of health of animals and safer food products.

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Expected Impact of Project Outcomes on Food Safety in Ontario:
Numerous outbreaks of foodborne illness have been attributed to post-process contamination of product due to inadequate sanitation of food contact surfaces. As well as reducing the burden of illness, more effective sanitation protocols will lead to substantial savings to governments and companies, especially those exporting to the U.S., by reducing the number of outbreaks and recalls of meat products. Since January 2003, there have been 14 recalls of meat products in Canada; three due to contamination by Listeria monocytogenes and 11 caused by E. coli O157:H7. Thus, the development of novel, cost-effective strategies for minimizing pathogenic contamination of ready-to-eat foods is of significant importance. Major routes for secondary contamination are processing surfaces and utensils. Commonly used sanitizers very often are not effective against bacterial spores and biofilms. Besides, recent research has indicated that pathogens can acquire resistance to sanitizers and, as a result of such adaptation, cross-resistance to antibiotics has been observed. Emergence of multi-antibiotic resistant pathogens is a risk to animal and human health as well as to the safety of food products. Development of resistance to Antimicrobial Photodynamic Treatment (APDT) has not been reported, which makes this approach more attractive for investigation. Implementation of the proposed new approach for surface sanitation will result in an improvement to the quality of food as well as a decrease in possible economic losses due to spoilage and recalls. <P> For more information, please visit the <a href="; target="_blank">Ontario Ministry of Agriculture, Food & Rural Affairs (OMAFRA) Food Safety Research Program</a>.

Griffiths, Mansel
University of Guelph
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