Date of Award

12-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Committee Member

Dr. Angela M. Fraser, Committee Chair

Committee Member

Dr. Xiuping Jiang

Committee Member

Dr. Duncan Darby

Committee Member

Dr. Julia L. Sharp

Abstract

Acute gastroenteritis (AGE), a major cause of illness, results in 179 million AGE cases every year in the United States. AGE bacteria that have low-infectious dose include E. coli O157:H7 (<10-100 cells) and L. monocytogenes (<1000 cells). Because of their low-infectious dose and high environmental resistance, contaminated surfaces, such as the exterior surface of food packages, could be a source for disease transmission. Our aim was to determine the persistence of E. coli O157:H7 and L. monocytogenes on three packaging materials - oriented polyethylene terephthalate (OPET), oriented polypropylene (OPP), and nylon-6. Coupons (25 cm2) from each material were sterilized under ultraviolet light for 5 minutes. Spot and spread inoculation was done on treatment coupons with ca. 7 log CFU of a 3-strain-mixture of green fluorescent protein (GFP)-labeled E. coli O157:H7. All the coupons were incubated at Technical Association of the Pulp and Paper Industry-TAPPI standards. Surviving E. coliO157:H7 cells on duplicate coupons were recovered in saline at selected time intervals (0, 0.25, 0.5, 1, 2, 3, 5, 7, 14, 15 days). Surviving cells were enumerated on tryptic soy broth supplemented with ampicillin using the 3 tubes most probable number-MPN method described in the Bacteriological Analytical Manual. The experiment was performed in triplicate. The same procedure was carried out for 3-strain-mixture of rifampin-resistant (Rif)-L. monocytogenes using tryptic soy broth supplemented with rifampin for the MPN method. (GFP)-E. coliO157:H7 and (Rif)-L. monocytogenes survived on OPET, OPP, and nylon-6 for 15 days. The survival of E. coli O157:H7 was significantly different (p < 0.05) from the survival of L. monocytogenes between days 0.5-1, 1-2, and 3-5. The survival of both bacteria on all three materials were not significantly different (p > 0.05). E. coli O157:H7 and L. monocytogenes survived for over 2 weeks on OPET, OPP, and nylon 6, suggesting a highly contaminated outer surface of a food package could be a potential fomite for AGE outbreaks.

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