NEC: ongoing challenges (Session)

This was a packed NEC session. It moved from the microbiome to the bench, then to future trials, a national probiotic cohort, and the brain. One message ran through every talk: NEC is probably not one disease. Until we treat it as a group of subtypes, prediction, prevention and trials will keep struggling.

1. The influence of the microbiome on development of NEC

Daphne Klerk (Netherlands)

Daphne gave a clear tour of 15 years of NEC microbiome research.

• The early 16S era (2013–2017): Studies were small, but the pattern was consistent. Dysbiosis seemed to precede NEC, with a bloom of Gram-negatives (Gammaproteobacteria/Enterobacteriaceae, the family Klebsiella belongs to). The proposed mechanism was LPS → TLR4 → excessive inflammation.

  • Barbara Warner’s Lancet study (46 NEC cases, 3 US centres) found that differences emerged only after the first month of life. The signal was strongest in infants born before 27 weeks.

  • Christopher Stewart’s Newcastle group found that a Bifidobacterium-dominant community was associated with healthy outcomes. Bifidobacteria are good at digesting HMOs.

• The shotgun metagenomics era (2016 onwards): This method has strain-level and functional resolution, but it is more expensive and computationally harder.

  • Some studies linked particular E. coli strains to worse outcomes.

  • One study found a Klebsiella signal only about 2 days before diagnosis. It came with adhesion genes and faster replication rates.

• The study she called the most important so far: This was a prospective, longitudinal metagenomic study of 236 preterm infants in 3 NICUs, 48 of whom developed NEC.

  • A NEC-associated pattern (more Klebsiella, lower diversity) appeared only in late-onset NEC (>40 days).

  • No taxon, pathway, growth rate or virulence gene separated pre-NEC samples from controls.

  • Medication was the dominant force shaping the preterm gut microbiome. It outweighed gestational age and mode of delivery.

• Why the field is stuck: Studies are mostly single-centre and underpowered. They are confounded by medication and feeding. Geography also matters, because location affects the microbiome. And sites may not mean the same disease when they say “NEC”.

• The gut virome is an emerging area. There are hints of early- versus late-onset differences.

• Probiotics are most likely protective. They are also further evidence that microbes are involved. But NEC incidence doesn’t fall to zero, and the optimal strain combination is unknown.

• Her own cohort included 150 infants born <30 weeks or <1000 g, of whom 11 developed NEC. Routine probiotics were introduced partway through the study.

  • Microbial composition separated clearly by probiotic exposure.

  • Probiotics also changed gut function: bile acid profiles shifted in a way that matched the genetic profile of the supplemented strains.

  • No overall composition or diversity signal predicted NEC. Only a few species, including Klebsiella pneumoniae, were associated with risk.

Q&A, on postbiotics: Postbiotics gained interest after the FDA warning on live probiotics about three years ago. They are probably safer, but she expects less impact than from live probiotics, which act in the gut and produce active metabolites. The postbiotic literature is also fragmented into single-centre and mouse studies. She would rather the field focus on identifying the best probiotic strains.

Take-home messages:

• There is no universal pre-NEC microbial signature.

• Research should shift from composition to function, and to how the microbiome interacts with the developing immune system.

• Sites need to agree on NEC subtypes before running meaningful multicentre studies.

2. NEO-O-100: Dose-dependent effects of dexamethasone on epithelial injury in human intestinal epithelial cells

Parvesh Mohan Garg (USA)

Rationale: Steroids are standard anti-inflammatories in adult IBD, but we give none in NEC. Garg’s group tested how dexamethasone affects intestinal epithelium injured with LPS, using human fetal small-intestinal epithelial cells.

• Cell viability: LPS killed most of the cells. Low-dose dexamethasone preserved viability. High-dose dexamethasone was itself cytotoxic. The effect was U-shaped.

• Scratch (wound-healing) assay: Dexamethasone did not impair epithelial migration or wound closure.

• Griess assay (nitrite as a marker of inflammatory stress): Low-dose dexamethasone brought nitrite production back to baseline. This held at both LPS concentrations, including the higher one.

• Clinical follow-up (unpublished, in preparation): In their surgical NEC cohort, there was about a 20% mortality difference between infants who did and did not receive hydrocortisone around surgery.

Take-home message: In vitro, low-dose steroids protect injured gut epithelium and high doses harm it. This is hypothesis-generating only. Dosing translation and clinical studies are the next step.

3. Future studies in the field of NEC

Nicholas Embleton (UK)

Nick gave a broad, forward-looking talk.

Disclosures: He is the PI of an industry-sponsored enteral insulin trial. He has advised a US physician being sued for allegedly causing NEC by using a fortifier.

Context:

• NEC has been described for over 200 years. He cited Michael Obladen’s “150 years of fruitless search for the cause” and doubts a single cause will ever be found.

• More children in Europe and the developed world die from NEC than from leukaemia. Yet academic neonatology gets a fraction of paediatric oncology funding.

Challenges:

• Definitions and heterogeneity. NEC in a 24-week infant on day 10 is not the same disease as NEC in a 28-week infant on full feeds at day 30. He described two peaks: around days 10–12 before full feeds, and around 4–5 weeks in fully fed infants.

• Animal models mostly rely on hypoxia-ischaemia, which is probably not the main mechanism in preterm infants.

• Biomarkers have been slow to develop.

• Outcome definitions are soft:

  • Stage 2 NEC varies between units.

  • “Required surgery” is not the same as “received surgery”.

  • “Death from NEC” is often unclear, since an infant may die with NEC rather than from it.

Opportunities across four stages:

1. The at-risk infant (prediction and prevention): Multi-omics will matter (metabolomics, proteomics, transcriptomics), not the microbiome alone. “I was absolutely convinced we would find the microbiome signal for NEC… I don’t think we have any chance.”

2. The infant developing NEC (diagnosis):

   • Integrate physiology, vital signs, imaging, the electronic patient record and bedside omics, with longitudinal and clinically relevant AI.

   • Urine may be an underused sample: it is non-invasive and easier than stool, which lags hours to days behind the disease. A combination of I-FABP, L-FABP and TFF3 looks promising, as do tight-junction proteins.

   • Volatile organic compounds and calprotectin in stool are also candidates.

3. Confirmed NEC (treatment):

   • Surgical choices: timing, drain versus laparotomy, stoma versus anastomosis.

   • Remote ischaemic conditioning (Toronto/Southampton collaborations), now heading to clinical trials.

   • TLR4 blockade: HMOs such as 2'-FL, short-chain fatty acid metabolites, and the Hackam group’s Compound 34.

4. After NEC (the “NEC exposome”): Everything the infant goes through can affect brain outcomes: pain, loss of kangaroo care and closeness, interrupted breast milk, anaesthetics and excipients, metabolic disruption, long lines and parenteral nutrition.

Human milk:

• Fresh mother’s milk remains one of the most effective interventions.

• Donor milk may vary in protective potential, for example by its HMO and IgA patterns.

• Formula regulates about 75 components, compared with the vast bioactive repertoire of breast milk.

• Fresh breast milk contains roughly 10⁴–10⁷ cells/mL, many of them stem cells that can traffic to peripheral organs. That is potentially billions of cells per day, but only in fresh, warm milk.

Q&A:

• Most trial-ready intervention? Milk-derived stem cells. He also stressed supporting mothers to keep lactating while their infant is sick and nil by mouth, and building on oral (buccal) colostrum to give cells before full feeds restart.

• Abdominal X-rays? He is not optimistic. We have all seen florid NEC with an unremarkable film, and “pneumatosis” in infants who did fine. He sees more promise in intestinal ultrasound and NIRS.

Call to action: Join the ESPR NEC Special Interest Group, and involve parent organisations in designing research.

4. NEO-O-101: Probiotics and risks of death, NEC and sepsis in very preterm infants

Stefan Johansson (Sweden)

Disclosure: He is co-founder of the company supplying the probiotics used in Sweden.

Setting: After the 2020 ESPGHAN position paper, the Swedish Neonatal Society recommended probiotics for infants born at 28–31 weeks. Probiotics were to start in the first days of life and continue to 34 weeks PMA. Uptake rose quickly to about 65%.

Design:

• Swedish Neonatal Quality Register, 2017–2024.

• About 4,600 very preterm infants, of whom about one third were exposed.

• Composite outcomes, treating death as a competing risk.

• Poisson regression adjusted for birth year and key covariates, clustered by birth hospital.

• Sensitivity analyses with propensity-score matching and inverse probability weighting gave consistent results.

Results (probiotics vs none):

• A mediation analysis suggested much of the mortality reduction ran through less NEC.

• There was no association with sepsis.

• A national NICU survey found no reported cases of probiotic sepsis. The register doesn’t capture this outcome, and rare events cannot be excluded.

Limitations:

• The design is observational.

• The baseline risk was low; all infants were initially fed human milk.

• Outcome misclassification and immortal time bias are possible.

• The results should not be extrapolated to extremely preterm infants.

Q&A (France), on blood cultures: Sweden uses a single combined paediatric bottle, without separate anaerobic culture. The Karolinska lab has shown the strains are culturable and asks clinicians to note probiotic use on the request. In the Netherlands, aerobic and anaerobic cultures are routine. The questioner warned that few studies have used proper anaerobic culture, so “no probiotic sepsis” should be interpreted carefully. Johansson agreed: the risk is low, but it is real with any strain.

Take-home message: In real-world national data, routine probiotics in 28–31-week infants were associated with a large reduction in death and/or NEC. Surgical NEC almost disappeared, and there was no sepsis signal.

5. Long-term outcome of NEC survivors

Alexandre Lapillonne (France)

Lapillonne covered NEC and spontaneous intestinal perforation (SIP) together, since the literature often mixes them.

EPIPAGE-2 (French national cohort):

• 95 infants with NEC, 38 with SIP, and more than 3,000 controls; 85% were followed to 2 years.

• Death or disability: NEC 35%, SIP about 46%, controls 14%. The adjusted odds were about 2.4× for NEC and 3.1× for SIP. Most of the excess was in-hospital death.

• Developmental delay at 2 years (ASQ): SIP 71%, NEC about 50%, controls 44%. The difference was significant only for SIP.

• The domains affected differed:

  • SIP mainly affected gross motor skills (41% vs 13% in controls).

  • NEC mainly affected problem solving (26% vs 12%).

Unpublished two-centre SIP study (n = 29, perforation at median day 5):

• More than half died or had severe brain lesions.

• About two-thirds of brain lesions appeared or progressed after the perforation.

• GA, birth weight, antenatal steroids, blood culture, platelets and CRP did not predict lesions. The white cell count did. Median WBC was about 5 with normal ultrasound, 8.8 with IVH and 32 with white matter damage; each doubling of WBC was associated with about 6× higher odds of white matter damage.

• His hypothesis is that SIP has two phenotypes: a low-inflammation one that largely spares the brain, and a high-inflammation one with white matter damage.

Literature (four meta-analyses over 20 years, plus large cohorts):

• NEC raises the risk of neurodevelopmental impairment by about 1.4–1.9×, with no improvement over two decades.

• The risk applies to 29–32-week infants too, not only to the extremely preterm.

• Vision and hearing impairment are about 4× more likely; CP, motor delay and cognitive delay about 2×. Epilepsy and behaviour do not appear to be affected.

• Medical NEC carries little extra risk. Surgical NEC carries an odds ratio of about 1.8–2.9.

• In the ELGAN cohort, surgical NEC followed by late-onset sepsis carried the highest risk on brain-structure measures, roughly 8–9×.

• The IQ deficit persists to school age (6 and 9 years), mainly after surgical NEC.

Mechanism: inflammation as the gut–brain mediator.

• The injured gut sends danger signals (TLR4).

• These spread through the circulation and reach the blood–brain interface.

• Microglia are activated.

• Pre-oligodendrocytes fail to mature, which leads to diffuse hypomyelination (maturation arrest rather than cell death).

• Secondary disturbances follow in axonal and cortical development.

Experimental evidence supports this sequence. In TLR4-deficient mice, NEC does not cause brain injury. The severity of neuroinflammation tracks NEC severity, and inflammation alone can reproduce the lesions. Repeated inflammatory hits during the window of pre-oligodendrocyte vulnerability (chorioamnionitis, NEC, SIP, late-onset sepsis) add up.

In practice, there is no tested neuroprotective intervention after NEC. Three levers remain:

1. Prevent NEC.

2. Limit second hits, especially late-onset sepsis. Consider laparotomy over peritoneal drain.

3. Identify high-risk infants and provide structured neurodevelopmental follow-up.

Take-home messages:

• NEC is one of the strongest acquired predictors of impairment, with about 2× the risk overall.

• The risk is mostly driven by surgical NEC.

• SIP is not benign.

• White matter is the main target, and about a third of infants also have cerebellar injury.

Disclosure: This is an AI-assisted summary of the session, generated from a recording made by our team in attendance. We believe it is as accurate as our own notes would be, but please refer to the speakers’ original work before applying anything in clinical practice.