The Journal of Medical Microbiology, Vol 34, Issue 1 57-62, Copyright © 1991 by Society for General Microbiology
Genetic manipulation of Salmonella serotype Bovismorbificans to aromatic-dependence and evaluation of its vaccine potential in mice
T. K. Mukkur, B. A. Stocker and K. H. Walker
CSIRO Division of Animal Health, McMaster Laboratory, Glebe, New South Wales, Australia.
The generation of smooth aromatic-dependent Salmonella serotype
Bovismorbificans (Group C2, O6, 8) from a smooth wild-type parent strain by
transduction with phage P1, and conjugation with Salmonella serotype
Typhimurium carrying F'-8gal is described. The smooth aromatic-dependent S.
serotype Bovismorbificans was non-lethal for mice at an oral challenge dose
of 2 x 10(9) cfu (equivalent to 200 LD50 of the parent, wild-type strain).
The safety of the auxotrophic mutant was further substantiated by comparing
its multiplication kinetics in vivo with that of its virulent parent
organisms. Mice immunised with live, smooth aromatic-dependent S. serotype
Bovismorbificans by either the oral or intraperitoneal (i.p.) route were
protected against oral challenge with virulent S. serotype
Bovismorbificans; the degree of protection was significantly better (p less
than 0.05) at a challenge dose of 100 or 200 LD50 in mice receiving two
rather than one vaccination. In contrast, mice immunised with three doses
of the formalin-killed virulent, parent organisms by the i.p. route were
not protected, in spite of high antibody titres. Only those mice immunised
with the live, smooth aromatic-dependent S. serotype Bovismorbificans i.p.
developed significant (p less than 0.01-0.05) delayed-type
hypersensitivity.
