Abstract: To isolate and characterize the lytic bacteriophage that might be used in prevention and treatment of porcine postweaning diarrhea due to enterotoxigenic E. coli K88 （ETEC-K88）. E. coli expressing the K88 adhesin on their surface is a common cause of diarrhea in newborn and weaned piglets. Mixtures of 3 strains of ETEC K88 were used as hosts for isolation of phages in sewage from 22 pig farms. The isolated phage was characterized at the microbiological and molecular levels. The optimal multiplicity of infection （MOI）, one-step growth curve, Thermo- and pH stability,lytic effective in vitro of the isolated bacteriophage were investigated. One phages that lysed ETEC K88 was isolated by double-layer agar plate method and named PK88-4. The phage produced large, clear plaques. The electron microscope showed the phage had necks and contractile tails and therefore belonged to the Myoviridae. The estimated genome size was about 60 kb and the restriction enzyme fragments suggested that it was dsDNA. The optimal MOI was 0. 01. The phage was stable at pH 5 - 10 and under 60℃, and could kill 100% host strain within 2 hours with MOI higher than 0. 001. The new isolated phage, named PK88-4, are potential candidates for prophy- laxis and therapy of porcine post-weaning diarrhea due to ETEC K88.

Key words: Enterotoxigenic, E. coli K88, Lytic bacteriophage, Biological properties, Lytic activities

CLC Number: 

• S435