COLONIZATION OF THE CHICKEN TRACHEA BY AN AVIRULENT AVIAN ESCHERICHIA-COLI TRANSFORMED WITH PLASMID PHK11

Recombinant plasmid pHK11 was transformed into an avirulent, wild-type avian Escherichia coli (E. coli Av) in order to study the plasmid's e ffect on colonization of the chicken trachea. The transformant (E. col i Av+pHK11) produced colicin V (ColV), had type F1 fimbriae, and was m otile. The E. coli Av recipient possessed type F1 fimbriae but was non motile; it did nor produce ColV. Four-day-old chicks were inoculated i n the trachea with 100 mu l of an overnight culture (approximate to 10 (8) colony-forming units) of E. coli Av, E. coli Av+pHK11, or sterile brain-heart infusion (BHI) broth. A group of uninoculated chicks was a lso included. Samples of the trachea were taken on days 4 and 10 posti noculation and compared histologically and bacteriologically Birds ino culated with E. coli Av+pHK11 had enhanced tracheal colonization and s howed increased histologic changes as compared with those inoculated w ith E. coli Av or BHI broth or uninoculated controls. These results in dicate that production of ColV and motility enhance the colonization o f the trachea and may be involved in the cause of pathologic lesions.