The effects of 405-nm visible light on the survival of Campylobacter on chicken skin and stainless steel

Authors: Gunther, Nereus - Jack; Phillips, John; Sommers, Christopher

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2015
Publication Date: 5/13/2016
Citation: Gunther, N.W., Phillips, J.G., Sommers, C.H. 2016. The effects of 405-nm visible light on the survival of Campylobacter on chicken skin and stainless steel. Foodborne Pathogens and Disease. 13(5):245-250.

Interpretive Summary: A bacterium known as Campylobacter causes a very high number of cases of food-borne illness worldwide, and a primary route for the introduction of Campylobacter into the food system is through contamination of poultry products. Therefore, techniques to reduce the numbers of Campylobacter on poultry products are highly desirable. High intensity light treatments have been utilized to eliminate harmful bacteria within many different environments. One of the most common of these light treatments utilizes ultraviolet (UV) light. However, UV treatments are expensive and the type of light generated can be harmful to the people applying them. For this reason high intensity visible light (non-UV light) has been investigated as a better treatment for the elimination of harmful bacteria. Visible light is safer and cheaper to use compared to UV light. A specific wavelength of visible light, 405 nm, has been the subject of significant research. This type of light has shown good success in eliminating Campylobacter. However, the previous experiments utilized the 405 nm light under conditions that were not relevant to the environments in which Campylobacter species are found within poultry products. Our research recreated the conditions in which Campylobacter exists in poultry products or under poultry processing conditions. Under these “real-world” conditions the 405 nm light treatments were not as effective in eliminating the Campylobacter. Additionally, use of 405 nm light under these conditions required methods of application that were overly time consuming and generated undesirable heat. This is the first time that 405 nm light treatment has been evaluated under realistic conditions against Campylobacter. The results suggest that this technology is not recommended for the reduction of this specific bacterial species on surfaces common to poultry products and poultry processing plants.

Technical Abstract: Campylobacter spp. are major food-borne pathogens responsible for a significant portion of the human cases of bacterial mediated gastrointestinal disease, and poultry products are an important source of infections. Reducing the numbers of this pathogen on poultry products should lower the incidence of Campylobacter-associated illness. Research has investigated the use of UV light for inactivating Campylobacter on poultry products or poultry processing environments. However, concerns about overall safety and cost have made UV technology less attractive to use by industry. More recently the use of high intensity visible 405 nm light has been proposed as a method for eliminating pathogenic bacteria. This study investigated the ability of 405 nm light to reduce the numbers of Campylobacter jejuni and Campylobacter coli under conditions similar to those found during poultry processing. A range of 405 nm light doses were applied to cocktails of six C. jejuni or six C. coli strains suspended in chicken exudate at 10 degrees C to minimize thermal effects. The exudates were placed onto chicken skins or food grade stainless steel coupons before being treated with the 405 nm light. Little difference was observed between C. jejuni and C. coli in exudate on poultry skin with only small average reductions of 1.7 log CFU/ml and 2.1 log CFU/ml, respectively, at the maximal experimental dose of 184-186 J/cm2. More noticeable differences were observed when the samples were placed on stainless steel with a dose of 89 J/cm2, producing an average reduction of 3.1 log CFU/ml for C. coli but only 1.1 log CFU/ml for C. jejuni. The maximal dose (181-183 J/cm2) on stainless steel produced sizable reductions for C. jejuni and C. coli of 4.9 and 5.1 log CFU/ml, respectively. Overall, 405 nm light for the reduction of Campylobacter under conditions similar to poultry processing required impractical exposure times to produce sufficiently lethal light doses and the largest observed reductions in Campylobacter numbers may have resulted from thermal effects when sample surfaces exceeded 50 degrees C.