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Salmonella does not just tolerate your gut's inflammation, it exploits it: it out-competes your good bacteria for zinc using a special uptake pump that defeats the immune system's metal-starvation defense.
Salmonella enterica is the species behind essentially all human Salmonella disease, spanning typhoid fever and non-typhoidal gastroenteritis. It invades host cells with type III secretion systems and thrives in the inflamed gut by defeating the host's metal-withholding defenses, a nutritional-immunity battle that is also its weak point.
Microbiome-targeted interventions (MBTIs) are validated using a dual-evidence logical framework. First, the intervention must realign the condition’s microbiome signature by increasing beneficial taxa that are consistently depleted and reducing pathogenic taxa that are consistently enriched. Second, the intervention must demonstrate measurable clinical benefit. Concordance of these effects in the same context validates the intervention as an MBTI and supports the clinical relevance of the microbiome signature.
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreSalmonella enterica is the species responsible for essentially all human Salmonella disease. It is a Gram-negative, facultatively anaerobic, flagellated rod in the Enterobacteriaceae, and it is divided into more than 2,000 serovars: the typhoidal serovars (Typhi, Paratyphi) cause typhoid fever, while the many non-typhoidal serovars cause gastroenteritis and invasive disease.[1] Invasive non-typhoidal Salmonella alone caused an estimated 535,000 cases and 77,500 deaths in 2017, hitting young children, elderly people, and people with HIV hardest.[2] On this database it appears as a differentially abundant taxon across human microbiome studies, usually a low-abundance signal rather than active infection.
What makes Salmonella distinctive is how it turns host defenses to its own advantage. It invades and survives inside host cells using two type III secretion systems, and it actually thrives in the inflamed gut, exploiting inflammation and outcompeting the resident microbiota.[1][3] Part of that edge is a metal-acquisition system that defeats the host's nutritional immunity, which is exactly the lens this database reads pathogens through.[3]
Salmonella are Gram-negative, facultatively anaerobic, non-spore-forming rods, typically motile by peritrichous flagella, in the family Enterobacteriaceae.[1] They tolerate bile and acid well enough to survive stomach passage and colonize the intestine, and are readily transmitted through contaminated food and water.[2]
Salmonella is a true pathogen rather than a commensal. Non-typhoidal serovars cause self-limiting gastroenteritis in healthy people but invasive, often bloodstream, disease with high mortality in vulnerable hosts (all-age case fatality around 14.5 percent),[2] while typhoidal serovars cause systemic typhoid fever.[1] A low-abundance differential signal in a microbiome study reflects an ecological shift or carriage, not necessarily active infection.
Salmonella's toolkit is built around invading and surviving inside host cells and winning the fight for nutrients in the inflamed gut.
| Virulence factor | Description and role |
|---|---|
| SPI-1 type III secretion system | Injects effectors that force host cells to engulf the bacterium, driving invasion of the intestinal epithelium.[1] |
| SPI-2 type III secretion system | Delivers a second set of effectors that let Salmonella survive and replicate inside a membrane-bound vacuole within host cells.[1] |
| Flagella and fimbrial adhesins | Peritrichous flagella and fimbriae mediate motility and attachment to the gut epithelium.[1] |
| Typhoid toxin and Vi antigen | Typhoidal serovars carry the typhoid toxin, which contributes to symptoms, and the Vi capsular antigen, which aids immune evasion.[1] |
| High-affinity zinc uptake (ZnuABC) | Lets Salmonella overcome host metal withholding and outgrow competing commensals in the inflamed gut.[3] |
Multidrug-resistant Salmonella, in both typhoidal and non-typhoidal serovars, is a growing problem that complicates treatment of typhoid fever and invasive disease.[1][2] Definitive treatment is susceptibility-guided; this page describes the organism's biology and its microbiome associations, not a treatment protocol.
Salmonella is a textbook case of a pathogen defeating nutritional immunity, and it does so by turning inflammation into an advantage.
| Metal / ion | Key features in Salmonella |
|---|---|
| Zinc (Zn) | The host neutrophil protein calprotectin sequesters zinc to starve microbes, but Salmonella's high-affinity ZnuABC importer overcomes this. As a result it thrives in the inflamed gut and outcompetes commensals; a ZnuABC mutant is rescued only when calprotectin is absent.[3] |
| Inflammation as opportunity | Rather than being suppressed by gut inflammation, Salmonella exploits it: inflammation shifts the metal and nutrient economy in ways the pathogen is equipped to win.[3] |
Read through the nutritional-immunity lens, the systems that give Salmonella its edge in the inflamed gut are also its openings.
| Weak point | Why it is exploitable |
|---|---|
| ZnuABC dependence | Because Salmonella relies on ZnuABC to beat calprotectin's zinc sequestration, reinforcing metal withholding or blocking that transporter attacks a system it needs to thrive.[3] |
| Colonization resistance | A healthy, intact microbiota resists Salmonella; the pathogen exploits inflammation to break that resistance, so protecting the barrier and community limits it.[3] |
| Susceptibility-guided therapy | Definitive treatment is antibiotics chosen by susceptibility, though rising resistance makes this harder.[2] |
For a pathogen, an intervention is anything that clears it or blunts its advantage. Clinical treatment is antibiotics managed by clinicians; the entries below are classified by our validation method, and this is not medical advice. The microbiome through-lines are colonization resistance and nutritional immunity.
| Intervention | Class | Status |
|---|---|---|
| Susceptibility-guided antibiotics | Drug | Validated |
| Colonization resistance (healthy microbiota) | Concept | Validation In Progress |
| Metal-withholding (zinc) support | Concept | Validation In Progress |
| Intervention | Mechanism |
| Susceptibility-guided antibiotics | Standard of care for invasive disease and typhoid, chosen by susceptibility as resistance rises.[2] |
| Colonization resistance | An intact microbiota competes with Salmonella and resists its colonization; the pathogen must break this to establish.[3] |
| Metal-withholding support | Reinforcing host zinc sequestration targets the ZnuABC system Salmonella uses to thrive in the inflamed gut.[3] |
Unnecessary disruption of the resident microbiota (for example needless broad-spectrum antibiotics), which weakens the colonization resistance that normally keeps Salmonella out.[3]
Where Salmonella (NCBI:txid28901) appears as a differentially abundant taxon across the Microbiome Medicine corpus. Each row aggregates every experiment in which the organism moved in a given condition; direction is its change in the case/exposure group, and grade is the strongest single study's methodology weight (A·D·S·C·R), the same engine that grades every signature on this site.
Across 6 conditions and 6 studies, the signal is genuinely mixed: enriched in 3, depleted in 3, and direction-conflicting in 0 (directional agreement 0.57). Because S. enterica is a low-carriage pathogen rather than a stable resident, its appearances here are best read as ecological signals or carriage, not infection, so the aggregate evidence tier is Low.
How to read these. Salmonella is not a normal stable resident of the gut, so a low-abundance differential signal usually reflects transient carriage, exposure, or an ecological shift rather than active infection. Detection resolves S. enterica as a species but not its serovar, which matters because typhoidal and non-typhoidal serovars differ greatly in behaviour and risk. This is why direction can conflict between cohorts and the aggregate tier stays Low.
Internal summaries of the 5 studies we reviewed in which Salmonella was a differential taxon across this corpus.
This study examined how the gut microbiome and serum metabolome differ between people with lactose intolerance (LI) and those without it. The researchers combined a paired-sample analysis of American Gut Project (AGP) data with metagenomic and untargeted metabolomic analyses in a separate cohort. They also performed fecal microbiota transplantation (FMT) experiments to test whether the LI-associated gut microbiome could influence inflammatory outcomes. The goal was to characterize the interaction between gut microbiota and circulating metabolites in LI.
The study drew on two data sources: paired samples from the American Gut Project (AGP), a large public microbiome dataset, and a Chinese cohort in which metagenomic and metabolomic profiling was performed. The abstract does not give exact sample sizes for either group. FMT experiments were also conducted, implying an animal model component, though further details are not specified in the abstract.
Fourteen microbial genera differed significantly between LI and control individuals in the AGP data. In the Chinese cohort, a machine learning approach identified seven bacterial species and nine metabolites that could distinguish the two groups. Notably, increased Escherichia coli in the LI group was negatively correlated with several metabolites, including PC (22:6/0:0), indole, and Lyso PC, while reduced levels of Faecalibacterium prausnitzii and Eubacterium rectale were positively associated with other metabolic changes.
The findings suggest that lactose intolerance is accompanied by a distinct gut microbial and metabolic signature, not just a lactase enzyme deficiency. The rise in Escherichia coli alongside depletion of beneficial short-chain-fatty-acid producers like Faecalibacterium prausnitzii and Eubacterium rectale points to a shift toward a more pro-inflammatory microbial community. This raises the possibility that microbiome-targeted interventions could help manage LI-related gastrointestinal symptoms, and the FMT experiments support a causal link between this altered microbiome and inflammatory outcomes.
This study used metagenomic sequencing to examine how chemotherapy affects the gut microbiota and antibiotic resistance genes (ARGs) in patients with acute leukemia (AL). Researchers compared stool samples collected before and after chemotherapy to track shifts in microbial composition and resistance gene carriage. The analysis also explored how antibiotic dosage shapes microbiota and ARG networks, and how gut microbial species relate to circulating inflammatory markers.
The subjects were patients diagnosed with acute leukemia who provided stool samples both before and after undergoing chemotherapy. The abstract does not give an exact number of patients, so the precise cohort size cannot be stated. Blood samples from these same patients were also analyzed for inflammatory biomarkers alongside the paired stool metagenomes.
Post-chemotherapy stool samples showed decreased alpha diversity and greater sample-to-sample dispersion compared with pre-chemotherapy samples, along with shifts in the abundance of specific bacterial taxa. Enterococcus, Klebsiella, and Escherichia coli were identified as the most prevalent carriers of antibiotic resistance genes. Correlation analysis linked specific microbial species to inflammatory markers, including C-reactive protein (CRP) and adenosine deaminase (ADA), and co-occurrence networks connected 179 microbial and ARG nodes across 206 edges. Treatment with cephamycin and sulfonamide antibiotics was associated with the emergence of multidrug-resistant Klebsiella colonization.
The findings suggest that chemotherapy in acute leukemia patients disrupts gut microbial balance in ways that favor colonization by resistant, potentially pathogenic Enterobacteriaceae members such as Klebsiella and E. coli. The observed links between specific antibiotics, resistant bacteria, and inflammatory biomarkers highlight the need for careful antibiotic selection and dosing during leukemia treatment to limit multidrug-resistant colonization. These data support closer monitoring of gut microbiota and ARG dynamics as a tool for anticipating infection risk and inflammatory complications in immunocompromised leukemia patients.
This study examined how delivery mode shapes the early gut microbiota of newborns using high-resolution shotgun sequencing. Researchers tracked the composition and dynamics of the neonatal gut microbiome over the first month of life. The design specifically compared elective cesarean section against vaginal delivery to sidestep the confounding effect of emergency cesareans, which can muddy conclusions about delivery mode's true influence.
The cohort consisted of Tunisian newborns, with stool samples collected from 5 infants born by elective cesarean section and 5 born vaginally. Samples were taken longitudinally at Day 0, Day 15, and Day 30 after birth. This is a small, delivery-mode-stratified newborn cohort rather than a large population sample.
Bacterial richness and diversity were similar between the elective cesarean and vaginally delivered groups, and both showed a shift in microbiota community composition during the first two weeks regardless of delivery mode. Both groups were dominated by Proteobacteria, Actinobacteria, and Firmicutes. However, starting from the second week, cesarean-delivered infants showed an underrepresentation of Bacteroides alongside an enrichment of opportunistic pathogenic species belonging to the ESKAPE group.
The findings suggest that even elective, non-emergency cesarean delivery is associated with a distinct early gut microbiota signature marked by Bacteroides depletion and ESKAPE pathogen enrichment, not merely overall diversity differences. This points to delivery mode as an independent driver of neonatal microbiome composition beyond confounding clinical circumstances. The emergence of opportunistic ESKAPE species by two weeks of age raises questions about potential vulnerability to opportunistic infection in cesarean-born infants that merit further, larger-scale investigation.
This study examined the gut microbiota of patients with COVID-19 pneumonia using 16S rRNA gene sequencing performed on rectal swabs. Researchers compared microbial composition and diversity between patients treated in the intensive care unit (i-COVID19), patients treated in infectious disease wards (w-COVID19), and healthy controls (CTRL). The goal was to characterize how gut microbial communities differ across varying levels of COVID-19 disease severity.
The study population consisted of patients hospitalized with COVID-19 pneumonia, divided into two groups by care setting: those admitted to the intensive care unit and those managed in infectious disease wards. These two patient groups were compared against a control group without COVID-19. The abstract does not report exact sample sizes, ages, or other demographic details for these cohorts.
Patients in the ICU showed a decrease in the Chao1 index compared to both controls and ward patients, indicating lower microbial richness in the most severely ill patients, while the Shannon index showed no significant change. At the phylum level, ward patients showed an increase in Proteobacteria compared to controls. Fusobacteria and Spirochetes were both decreased relative to controls, with Spirochetes showing the greatest decrease in ICU patients specifically.
The findings indicate that gut microbial communities shift in composition and richness according to COVID-19 disease severity, with the most pronounced changes occurring in critically ill ICU patients. These preliminary results suggest the gut microbiota may hold promising biomarkers for diagnosing COVID-19 and gauging disease severity. The authors note that validation in larger cohorts could support using microbiota profiles to help stratify patients by severity.
This study examined the early development of the gut microbiome in young children carrying high genetic risk for type 1 diabetes (T1D). Researchers used high throughput 16S rRNA gene sequencing on monthly stool samples collected from 4 to 6 months of age until 2.2 years of age. The goal was to identify compositional changes in the gut microbiome that occur before children develop T1D related autoimmunity. Both low abundance taxa and highly abundant groups, including two closely related Bacteroides species, were assessed for their relationship to later seroconversion.
The cohort consisted of 76 children at high genetic risk for T1D, all born in the same hospital in Turku, Finland. Of these children, 29 later seroconverted to T1D related autoimmunity, and 22 of those went on to develop T1D, forming the case group. The remaining 47 children stayed healthy throughout the study period and served as controls.
Several low abundance bacterial species showed significant compositional differences between children who later seroconverted and those who remained healthy. Notably, a highly abundant group made up of two closely related species, Bacteroides dorei and a related Bacteroides species, stood out as dominant in the gut microbiome prior to the onset of autoimmunity. This finding points to an early, high abundance microbial signal associated with the path toward T1D related autoimmunity, distinct from the more subtle low abundance differences.
The early presence and dominance of Bacteroides dorei before autoimmune seroconversion suggests the gut microbiome may play an active role in the processes leading to T1D in genetically susceptible children. Because the sampling began in infancy and continued monthly, these findings support the idea that microbiome monitoring during early childhood could help identify children at elevated risk before clinical autoimmunity appears. This work adds to the broader case that environmental factors, particularly the developing gut microbiome, interact with genetic predisposition to influence autoimmune disease risk. The Salmonella and Enterobacteriaceae groups were not mentioned in this abstract, so no claims are made about them here.
2026-07-04
Salmonella enterica majorTaxon page created: biology (morphology, pathogenicity, type III secretion virulence, antibiotic resistance), the zinc / nutritional-immunity metallome and vulnerabilities, interventions, the data-derived Conditions table across 6 conditions, and the full research feed.
Johnson R, Mylona E, Frankel G.
Typhoidal Salmonella: distinctive virulence factors and pathogenesis.Cell Microbiol. 2018
GBD 2017 Non-Typhoidal Salmonella Invasive Disease Collaborators.
The global burden of non-typhoidal salmonella invasive disease: a systematic analysis for the Global Burden of Disease Study 2017.Lancet Infect Dis. 2019
Liu JZ, Jellbauer S, Poe AJ, et al. (Raffatellu M).
Zinc sequestration by the neutrophil protein calprotectin enhances Salmonella growth in the inflamed gut.Cell Host Microbe. 2012
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