A limited role for SsrA/B in persistent Salmonella Typhimurium infections in pigs.
Virulence genes regulated by the SsrA/B system are indispensable for systemic disease in BALB/c mice. The role of this regulating system in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. In the present study, the interactions of Salmonella Typhimurium and an ssrA/B mutant were compared in vitro and in vivo. The ssrA/B mutant strain displayed decreased Salmonella Pathogenicity Island 2 (SPI-2) expression levels, showed a replication defect in mouse macrophages and was attenuated in a mouse model after oral inoculation. Using real time qRT-PCR and a porcine ileal loop model, it was shown that the ssrA/B mutant strain was not significantly attenuated in overall virulence and SPI-1 expression in specific. Flowcytometric analysis demonstrated that the ssrA/B mutant strain was defective in intracellular replication in porcine macrophages. After oral inoculation of piglets with the wild type strain or the ssrA/B mutant strain, the animals of both groups excreted Salmonella and were colonized by Salmonella to the same extent. In an intravenous mixed infection model, the ssrA/B mutant strain was defective in the colonization of several internal organs. These results suggest that the ssrA/B gene of Salmonella Typhimurium plays a limited role in the persistent intestinal colonization of pigs.
Boyen
Filip
F
Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium. filip.boyen@UGent.be
Pasmans
Frank
F
Van Immerseel
Filip
F
Morgan
Eirwen
E
Botteldoorn
Nadine
N
Heyndrickx
Marc
M
Volf
Jiri
J
Favoreel
Herman
H
Hernalsteens
Jean-Pierre
JP
Ducatelle
Richard
R
Haesebrouck
Freddy
F
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D005260:Female; D005434:Flow Cytometry; D015964:Gene Expression Regulation, Bacterial; D044404:Genomic Islands; D007422:Intestines / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D009928:Organ Specificity; D012329:RNA, Bacterial / Q000235:genetics*; D011897:Random Allocation; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D014157:Transcription Factors / Q000235:genetics*; D014774:Virulence
D001426:Bacterial Proteins; D012329:RNA, Bacterial; C119761:SsrB protein, Salmonella typhimurium; D014157:Transcription Factors; C096222:tmRNA