Effect of antibodies to type 1 fimbriae on clearance of fimbriated Escherichia coli from the bloodstream of turkeys.

Young turkeys (n = 20) were inoculated IV with fimbriated, virulent Escherichia coli ECl (O78:K80: H9:F1). Blood samples were collected for bacterial quantitation at postinoculation minutes (PIM) 10, 20, 30, 40, 50, and 60. Immediately after the PIM 30 sampling, the turkeys were allotted into 4 groups (5 turkeys/group) and were injected IV with 1 of the following antisera: group 1, antibodies to F1 fimbriae (AF); group 2, antibodies to E coli O78 antigen (AO); group 3, antibodies to live, fimbriated (F1+) homologous E coli (ALEC); or group 4, normal turkey serum (NTS) collected from a healthy turkey. Compared with NTS, ALEC and AO caused a significant reduction in blood-borne E coli, whereas AF did not reduce bacterial numbers. In addition, 2 groups of 10 turkeys were inoculated IV with live, F1+ or nonfimbriated (F1-) E coli ECl. Numbers of viable bacteria were determined in blood samples and liver specimens collected 2 minutes after inoculation. Compared with F1- bacteria, significantly more F1+ bacteria were found in liver specimens and significantly fewer F1+ bacteria were found in blood samples. Results indicated that antibodies to F1 fimbriae do not enhance clearance of F1+ E coli from the bloodstream of turkeys probably because F1+ bacteria are selectively cleared by the liver, even without antibody.