The Journal of Medical Microbiology, Vol 39, Issue 4 268-272, Copyright © 1993 by Society for General Microbiology
Serological response of sheep to plasmid-encoded proteins of Yersinia species following natural infection with Y. enterocolitica and Y. pseudotuberculosis
R. M. Robins-Browne, A. M. Bordun and K. J. Slee
Department of Microbiology, Royal Children's Hospital, Parkville, Victoria, Australia.
A prospective study of the serological response to natural infection with
Yersinia enterocolitica and Y. pseudotuberculosis was performed in an
experimental flock of sheep. A preliminary investigation with
immunoblotting techniques showed that lambs infected with virulent Yersinia
spp. produced antibodies to several yersinia outer-membrane proteins (yops)
encoded by a virulence plasmid (pYV) of Y. enterocolitica or Y.
pseudotuberculosis. Thereafter, an enzyme immunoassay (EIA) was developed
to measure antibodies to yops. Criteria for interpreting the EIA were
established by examining sera from a negative control population of lambs
which had not been infected with Yersinia spp. since birth. Test samples
comprised 25 pairs of pre- and post-infection sera from animals with
bacteriologically proven infections with Yersinia spp. The results showed
that infection of lambs with pYV-bearing strains of Y. enterocolitica or Y.
pseudotuberculosis invariably evoked a significant antibody response to
yops, even though all the infections were subclinical. No animal infected
with so-called "environmental", pYV-negative Yersinia spp. seroconverted to
yops. EIA with yops as antigen provided a sensitive and specific means to
diagnose subclinical infection of lambs with virulent Yersinia spp.
