Enteric Salmonellosis Disrupts the Microbial Ecology of the Murine Gastrointestinal Tract

Abstract

The commensal microbiota protects the murine host from enteric pathogens. Nevertheless, specific pathogens are able to colonize the intestinal tract and invade, despite the presence of an intact biota. Possibly, effective pathogens disrupt the indigenous microbiota, either directly through pathogen-commensal interaction, indirectly via the host mucosal immune response to the pathogen, or by a combination of these factors. This study investigates the effect of peroral Salmonella enterica serovar Typhimurium infection on the intestinal microbiota. Since the majority of the intestinal microbiota cannot be cultured by conventional techniques, molecular approaches using 16S rRNA sequences were applied. Several major bacterial groups were assayed using quantitative PCR. Administration of either the 50% lethal dose (LD 50 ) or 10؋ LD 50 of Salmonella enterica serovar Typhimurium caused changes in the microbiota throughout the intestinal tract over the time course of infection. A 95% decrease in total bacterial number was noted in the cecum and large intestine with 10؋ LD 50 S. enterica serovar Typhimurium challenge at 7 days postinfection, concurrent with gross evidence of diarrhea. In addition, alterations in microbiota composition preceded the onset of diarrhea, suggesting the involvement of pathogen-commensal interactions and/or host responses unrelated to diarrhea. Microbiota alterations were not permanent and reverted to the microbiota of uninfected mice by 1 month postinfection. Infection with a Salmonella pathogenicity island 1 (SPI1) mutant did not result in microbiota alterations, while SPI2 mutant infections triggered partial changes. Neither mutant was capable of prolonged colonization or induction of mucosal inflammation. These data suggest that several Salmonella virulence factors, particularly those involved in the local mucosal host response, are required for disruption of the intestinal ecosystem.

The pathogenBatrachochytrium dendrobatidisdisturbs the frog skin microbiome during a natural epidemic and experimental infection

“…conditions (13,14,42,51,52), but are rarely documented during natural outbreaks of known infectious pathogens in the wild. A few studies have demonstrated associations between pathogen infection and bacterial diversity (53) or the abundance of certain cultured isolates in the field (39), but it is often challenging to determine whether observational correlations stem from microbiome variation affecting resistance to pathogen infection or, instead, from pathogen infection altering the microbiome.…”

“…The microbiome may interact with pathogens through competition for resources, release of antimicrobial compounds, contactdependent antagonism, or modulation of the host immune response (10), and an "imbalanced" microbiome may leave the host more susceptible to pathogen infection (11,12). At the same time, an invading pathogen may disrupt the microbiome (10,(13)(14)(15). Thus, the microbiome may play a role in disease resistance, or may itself be disturbed or altered by invading pathogens.…”

Ecto-Nucleoside Triphosphate Diphosphohydrolase 7 Controls Th17 Cell Responses through Regulation of Luminal ATP in the Small Intestine

“…Bacterial 16S rRNA genes extracted from luminal contents and epithelial surfaces were amplified by bacterial group-specific primers: all bacteria, 59-ACTCCTACGGGAGG-CAGCAGT-39 and 59-ATTACCGCGGCTGCTGGC-39; Lactobacillaceae, 59-AGCAGTAGGGAATCTTCCA-39 and 59-CACCGCTACACATGGAG-39; segmented filamentous bacteria (SFB), 59-GACGCTGAGGCATGA-GAGCAT-39 and 59-GACGGCACGGATTGTTATTCA-39; Bacteroides, 59-GGTTCTGAGAGGAAGGTCCC-39 and 59-GCTGCCTCCCGTAG-GAGT-39; and Clostridiales, 59-ACTCCTACGGGAGGCAGC-39 and 59-GCTTCTTAGTCAGGTACCGTCAT-39 (31,32). All reactions were performed in 20 ml using SYBR Green I Master Mix (Roche).…”

Homeostatic IL-23 receptor signaling limits Th17 response through IL-22–mediated containment of commensal microbiota

“…Quantitation of bacteria abundance was performed with an ABI real-time PCR system detecting SYBR (Applied Biosystems). Primers and PCR condition used were as described (26,27) and are listed in Table S3. Further details are provided in SI Materials and Methods.…”