Competitive Exclusion of Escherichia Coli O157

Competitive exclusion of Escherichia coli O157:H7 and coliforms by Lactococcus lactis isolated from radish [Raphanus sativus] sprouts.

Journal of Antibacterial and Antifungal Agents, Japan (Japan) (Jul 2002.)v. 30(7) p. 405-413.

Okuda, T. (Sanwa Norin Co. Ltd., Hasuda, Saitama (Japan)); Uchida, H.; Nakamura, M.; Endo, A.; Okada, S.


Since 1990, a number of food poisoning cases involving fresh edible sprouts have occurred on a large scale throughout the world, and safety measures against such outbreaks have been strongly called for. In this research, an attempt was made to use lactic acid bacteria to secure the safety of radish sprouts. As lactic acid bacteria, 4 types of bacteria consisting of Lactococcus lactis SNW-1, isolated from radish sprouts, and Lactobacillus casei subsp casei NRIC1917, L. pentosus SNRIC1609 and L. plantarum NRIC1553, isolated from other plants, were used. Those strains were each examined for colony development on the seeds and acid productivity in a growing test. As a result, it was found that L. lactis SNW-1 was clearly superior to the other strains in terms of acid productivity and colonization ability. In a culturing test of those strains mixed with Escherichia coli O157:H7 and coliforms, a lapse of time dependent on the mixing ratio was observed in every strain, while finally only L. lactis SNW-1 was detected. When this strain was actually used in the growth of radish sprouts, a significant decrease in the number of coliform colonies was observed in the stage of the final product. This fact indicates that radish sprouts grown with L. lactis SNW-1 may result in the exclusion of pathogenic bacteria such as E. coli O157:H7.