Affiliation:
1. Division of Microbiology, Institute for Animal Health, Compton, Berkshire RG20 7NN, United Kingdom
Abstract
ABSTRACT
Salmonella enterica
serovar Dublin is a host-restricted serovar associated with typhoidal disease in cattle. In contrast, the fowl-associated serovar
S. enterica
serovar Gallinarum is avirulent in calves, yet it invades ileal mucosa and induces enteritis at levels comparable to those induced by
S. enterica
serovar Dublin. Suppression subtractive hybridization was employed to identify
S. enterica
serovar Dublin strain SD3246 genes absent from
S. enterica
serovar Gallinarum strain SG9. Forty-one
S. enterica
serovar Dublin fragments were cloned and sequenced. Among these, 24 mobile-element-associated genes were identified, and 12 clones exhibited similarity with sequences of known or predicted function in other serovars. Three
S. enterica
serovar Dublin-specific regions were homologous to regions from the genome of
Enterobacter
sp. strain 638. Sequencing of fragments adjacent to these three sequences revealed the presence of a 21-kb genomic island, designated
S. enterica
serovar Dublin island 1 (SDI-1). PCR analysis and Southern blotting showed that SDI-1 is highly conserved within
S. enterica
serovar Dublin isolates but rarely found in other serovars. To probe the role of genes identified by subtractive hybridization in vivo, 24 signature-tagged
S. enterica
serovar Dublin SD3246 mutants lacking loci not present in
Salmonella
serovar Gallinarum SG9 were created and screened by oral challenge of cattle. Though attenuation of tagged SG9 and SD3246
Salmonella
pathogenicity island-1 (SPI-1) and SPI-2 mutant strains was detected, no obvious defects of these 24 mutants were detected. Subsequently, a ΔSDI-1 mutant was found to exhibit weak but significant attenuation compared with the parent strain in coinfection of calves. SDI-1 mutation did not impair invasion, intramacrophage survival, or virulence in mice, implying that SDI-1 does not influence fitness per se and may act in a host-specific manner.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
15 articles.
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