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Infect Immun, April 1998, p. 1432-1438, Vol. 66, No. 4
Institute for Animal Health, Compton,
Newbury, Berkshire RG20 7NN, United Kingdom
Received 22 August 1997/Returned for modification 8 October
1997/Accepted 22 December 1997
The induction of secretory and inflammatory responses in calves by
Salmonella typhimurium and Salmonella dublin
strains was compared, and the effects of mutations in the
invH and stn genes were assessed. S. typhimurium induced greater secretory and inflammatory responses
than S. dublin in bovine ileal loops, despite the fact that
these serotypes were recovered from bovine ileal mucosa in comparable
numbers (P. R. Watson, S. M. Paulin, A. P. Bland,
P. W. Jones, and T. S. Wallis, Infect. Immun. 63:2743-2754,
1995). These results implicate serotype-specific factors other than, or
in addition to, intestinal invasion in the induction of enteritis. The
secretory and inflammatory responses induced by S. typhimurium and S. dublin in bovine ligated ileal
loops were not significantly altered by mutation of stn,
which suggests that stn does not have a major role in
Salmonella-induced enteritis. The invH mutation significantly reduced the secretory and inflammatory responses induced
in bovine ileal loops, and this correlated with a reduction in the
severity of enteritis following oral inoculation of calves. The
attenuation associated with the invH mutation did not
appear to be due to an increased susceptibility to the innate host
defense mechanisms, because the resistance of S. typhimurium to the bactericidal action of either bovine
polymorphonuclear leukocytes or bovine serum was not significantly
altered. However, lysis of macrophages following infection with
S. typhimurium was significantly reduced by the
invH mutation. The invH mutation prevented the
normal secretion of several proteins, including SipC, by S. typhimurium, indicating that the function of the
inv-spa-encoded type III protein secretion system was
disrupted. Taken together, these observations implicate inv-spa-dependent effectors in mediation of
Salmonella-induced enteritis in cattle. Clearly, however,
other undefined serotype-specific virulence factors are also involved
in Salmonella-induced enteritis.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutation of invH, but Not
stn, Reduces Salmonella-Induced Enteritis
in Cattle
*
Corresponding author. Mailing address: Institute for
Animal Health, Compton, Newbury, Berkshire RG20 7NN, United Kingdom. Phone: (01635) 578411. Fax: (01635) 577263. E-mail:
timothy.wallis{at}BBSRC.ac.uk.
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