Can Gut Bacteria Predict Whether Infliximab Works? A 2026 Review of the Evidence in Children With IBD

Why Predicting Infliximab Response Matters

Infliximab is among the most widely used biologic medicines for children with moderate-to-severe Crohn's disease or ulcerative colitis. It works by blocking tumour necrosis factor-alpha (TNF-alpha), a protein that plays a central role in driving intestinal inflammation in IBD. A Cochrane systematic review of TNF-alpha antagonists in paediatric Crohn's disease confirmed both their efficacy and their established place in treatment pathways (Hyams JS et al., Cochrane Database Syst Rev).

However, a real clinical challenge persists: around one in three children who start infliximab do not achieve adequate disease control. This is called primary non-response, and it means families and clinical teams spend months on a treatment that ultimately does not work before pivoting to an alternative.

The ability to predict before the first infusion which children are likely to respond could transform the clinical experience: fewer months on an ineffective drug, earlier access to better-matched alternatives, and more informed conversations between families and specialist teams.

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What the Systematic Review Investigated

A 2026 systematic review by Altaher H, Al-Mashhadani M, Usman R, Ghelani H, and Jan RK, published in Frontiers in Pharmacology, examined whether gut microbiome signatures could serve as candidate biomarkers for predicting infliximab treatment response in children with IBD (Altaher H et al., Frontiers in Pharmacology, 2026).

The gut microbiome refers to the community of bacteria, fungi, viruses, and other microorganisms that live in the digestive tract. In IBD, this microbial ecosystem is known to be disrupted (a state called dysbiosis), and researchers have long suspected that these disruptions may interact with the immune pathways that biologic drugs target.

The review systematically identified and analysed published studies that measured gut microbiome composition or function in paediatric IBD patients before infliximab treatment, and then tracked whether those microbial profiles correlated with clinical outcomes after infliximab was started.

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Candidate Biomarkers: What the Evidence Shows

The review identified a body of evidence linking specific baseline gut microbiome patterns (the bacterial signatures present before infliximab is started) to whether infliximab subsequently achieved disease control.

Certain bacterial patterns appeared more consistently in patients who responded well to infliximab; others appeared more common in patients who did not respond. These patterns are measurable from a stool sample, which represents a non-invasive and relatively practical approach compared with tissue sampling.

The authors described these findings as "candidate biomarkers." This careful term reflects the current state of the evidence: these signals have been observed across multiple studies and are real and reproducible enough to warrant systematic review, but candidate status means the markers have not yet cleared the validation hurdles required before clinical use. Large-scale prospective studies in diverse populations, standardised microbiome measurement methods, and agreed clinical thresholds are all still needed.

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Why the Gut Microbiome May Be Linked to Infliximab Response

IBD involves complex interactions between the immune system, the gut lining, and the microbial community living within it. Infliximab targets a specific inflammatory signalling pathway, but the broader microbial environment appears to modulate how well that pathway is suppressed and how the gut lining heals.

Some bacterial species produce compounds that interact with immune cells; others influence the gut mucosal barrier; others affect how drugs are metabolised. The result is that the same dose of infliximab, in two patients with otherwise similar disease profiles, may achieve very different outcomes depending on what microbes are present and what metabolic functions they are performing.

This biological rationale makes the microbiome a plausible window into treatment response, and helps explain why this line of research has attracted growing attention.

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What This Research Does Not Show

Several important boundaries apply to this research.

First, this is a systematic review of observational associations. The studies included observed that certain microbiome patterns correlated with infliximab response; they do not prove that the microbiome caused the response or non-response.

Second, this evidence does not support the idea that changing the gut microbiome through specific diets, probiotics, or other interventions will improve infliximab response. The associations are descriptive, not prescriptive.

Third, gut microbiome testing to predict infliximab response is not currently part of standard clinical care for paediatric IBD. No validated clinical test based on these findings is yet in routine use.

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What Comes Next in Research

Translating candidate biomarkers into clinical tools requires prospective validation studies that test the markers in new patient populations, confirm their predictive accuracy, and establish how they would integrate into clinical decision pathways. Standardising microbiome measurement is also an active challenge: different laboratories use different methods, making it difficult to compare results across studies.

Research into the gut microbiome as a treatment response predictor in IBD is growing, and paediatric IBD specifically is an area of active focus. Whether these candidate markers will eventually reach clinical use depends on the results of that ongoing work.

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Source: Altaher H, Al-Mashhadani M, Usman R, Ghelani H, Jan RK. Infliximab-linked gut microbiome signatures as candidate treatment response biomarkers in pediatric inflammatory bowel disease: a systematic review. Frontiers in Pharmacology. 2026. https://pubmed.ncbi.nlm.nih.gov/42499495/

Context source: Hyams JS et al. Tumor necrosis factor-alpha antagonists for treatment of pediatric Crohn's disease. Cochrane Database of Systematic Reviews. https://pubmed.ncbi.nlm.nih.gov/40747801/

Consult your doctor. If your child has been recommended infliximab for inflammatory bowel disease, discuss the full treatment plan and monitoring schedule with their paediatric gastroenterologist. Gut microbiome testing to predict biologic response is not currently standard care. Never adjust or stop infliximab therapy without medical guidance.