Effect of UV- C radiation on survival of Escherichia coli O157: H7 inoculated fish fillets from fresh water and marine sources

Abstract

Radiation technique using UV-C was applied in this study on freshwater Nile tilapia fish (Oreochromis niloticus) and marine-water Japanese threadfin bream fish (Nemipterus japonicas) fillets injected by Escherichia coli strain O157:H7. Tilapia fish (average weight and length are 150 ± 10 g, 15 ± 5 cm, respectively) and threadfin bream (average weight and length are 120 ± 5 g and 15 ± 2 cm, respectively) were collected from fresh fish market at Suez, Egypt. Fish samples were filleted, injected with Escherichia coli strain O157:H7, and subjected to UV treatment (15W). Samples exposed to UV irradiation (monochromatic, 253.7 nm) at four different distances: 12, 24, 30 and 45 cm. Each UV-C radiation treatment was performed for 5, 10, 15, and 20 min. Maximum reduction in the total count of E. coli strain O157:H7 (1.82 logs CFU/g) was associated with threadfin bream marine fish samples treated at 45 cm for 20 min. While in tilapia samples, count of E. coli strain O157:H7 was reduced to 1.1 logs CFU/g when treated at 24 cm for 15 min. Therefore, this study recommends this simple method of radiation using UV-C as a successful technique to expand the safety of fish fillets from fresh water and marine sources.