Inhibition of Salmonella typhimurium in the chicken intestinal tract by a transformed avirulent avian Escherichia coli

An avirulent, wild-type avian Escherichia coli (E. coli Av) was electrotran sformed with a plasmid coding for the production of microcin 24 (pGOB18) an d was designated E. roll AvGOB18. The transformant inhibited the growth of seven serotypes of Salmonella commonly associated with colonization and con tamination of poultry products and seven strains of E. roll O157:H7 in the in vitro colicin/microcin assay. The transformant did not inhibit the repli cation of multiple isolates of Listeria monocytogenes or Campylobacter jeju ni in similar assays. The transformant is nonconjugative, indicating that t he plasmid would not be transmitted to other intestinal microflora in the e nvironment. The transformant also survived in sterile tap and deionized wat er incubated at 25 C and 37 C in the laboratory for 30 days and was recover ed from drinkers and birds in in vivo floor pen studies. In in vivo studies , E. coli AvGOB18 did not colonize the intestinal tract of broiler chicks w hen given as a single or multiple dose and did not reduce the Salmonella lo ad in the broilers. But Salmonella typhimurium was reduced significantly in the intestinal tracts of broiler chickens when E, roll AvGOB18 was adminis tered continually in the water supply.