Hannover Medical School January 25 th 2010 Salmonella enterica serovar Typhimurium exploits inflammation to compete with the intestinal microbiota Stecher et al., PLoS Biol 5(10): e

Hannover Medical School Salmonella enterica Gram-negative, rod-shaped, motile bacterium typically acquired by the oral ingestion of contaminated food or water many different serovars 1)typhoid  enteric fever e.g. serovar Typhi or Paratyphi 2)non-typhoid  gastroenteritis e.g. serovar Typhimurium

Hannover Medical School Intestinal microbiota more than 1000 species with a collective weight of about 1kg in human intestine symbiotic relationship with the host: 1. structual functions e.g. immune system development 2. metabolic functions e.g. synthesize vitamins 3. protective functions changed from O´Hara et al., EMBO reports, 2006  Role of inflammation for Salmonella colonization and competition against intrinsic microbiota

Hannover Medical School Colonization efficiency of Salmonella enterica serovar Typhimurium (S. Tm) in the streptomycin mouse model 1 day Streptomycin mouse model S. Tm wt  wild-type S. Tm avir  mutant that lacks virulence- associated type III secretion systems  S. Tm wt but not S. Tm avir can colonize the intestine and cause colitis

Hannover Medical School Colonization efficiency of S. Tm wt and S. Tm avir in the streptomycin mouse model sm = streptomycin; L = cecum lumen fluorescence microscopy of cecum tissue sections  S. Tm avir but not S. Tm wt is outcompeted by re-growing commensal microbiota

Hannover Medical School Microbiota manipulation by S. Tm in the streptomycin mouse model 16S rRNA gene sequencing of intestinal microbiota sm = streptomycin

Hannover Medical School Microbiota composition of individual mice (streptomycin mouse model) mouse sm = streptomycin 16S rRNA gene sequencing of intestinal microbiota  S. Tm wt infection alters the composition of intestinal microbiota

Hannover Medical School Competitive infection with Lactobacillus reuteri in the streptomycin mouse model  alteration of microbiota composition by S. Tm wt can be demonstrated at the level of a single bacterial strain L. retueri RR Rif  a commensal bacteria of mouse intestine L. retueri RR Rif infection 1 day p.i. with S. Tm

Hannover Medical School Influence of S. Tm wt induced inflammation on colonization of S. Tm avir in the streptomycin mouse model  S. Tm wt triggered colitis creates favourable conditions in the intestinal lumen that rescues S. Tm avir colonization Mixed infection with S. Tm wt also complements the colonization defect of S. Tm avir in a chronic Salmonella colitis model (129Sv/Ev mice)

Hannover Medical School Influence of cecal inflammation per se on S. Tm avir colonization C3H/HeJBir IL10-/- mice  lack anti-inflammatory IL-10; develop colitis spontaneously similar results were made using a C57Bl/6IL10 -/- mouse model Intestinal content

Hannover Medical School Influence of intestinal inflammation in the VILLIN-HA CL4-CD8 mouse model on S. Tm avir colonization VILLIN-HA CL4-CD8 mouse model Intestinal content  inflammation per se can enhance S. Tm avir colonization VILLIN-HA mice  express HA from influenza virus under the control of enterocyte- specific VILLIN promotor CL4 transgenic mice  express TCR that recognize HA epitope

Hannover Medical School Microbiota composition in the VILLIN-HA CL4-CD8 mouse model 16S rRNA gene sequencing of intestinal microbiota 4 days post adoptive transfer  inflammation per se does not drastically change the gut flora composition

Hannover Medical School Summary  S. Tm avir (T3SS deficient mutant) but not S. Tm wt is outcompeted by re-growing commensal microbiota in the streptmycin mouse model  Inflammation triggered by specific S. Tm virulence factors (T3SS), by genetic predisposition (IL10 -/- ), or by T cell-inflicted damage (VILLIN-HA CL4-CD8 model) can enhance S. Tm avir colonization

Hannover Medical School Microbiota-pathogen-host interaction model S. Tm virulence factors trigger colitis Inflammation shifts the growth competition in favour for the pathogen: a.inhibitory effects on the microbiota -release of antimicrobial factors -disruption of commensal network b.improved growth conditions for the pathogen -altered nutrient mix symbiotic interaction resident microbiota mediates colonization resistance against incoming S. Tm

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