Targeting a life-threatening gut condition in preterm babies

Currently 60,000 preterm babies are born every year in the UK[i] (worldwide, one in nine babies are born preterm[ii]). The earlier the birth, the more likely the baby is to develop necrotising enterocolitis (NEC), a devastating bowel illness that can require emergency surgery, is sometimes difficult to diagnose and is a leading cause of death in neonatal units; hundreds of preterm babies develop it every year, up to 35% of babies contracting NEC die, and those surviving often develop severe health problems[iii].

An abnormal gut microbiota is an important predisposing risk factor for NEC. Preterm babies often have a lower abundance of beneficial Bifidobacterium species than babies born at full-term; babies cannot adequately digest breast milk sugars without gut bacteria which break sugars down into simpler components that the baby can use.

Staff from Quadram Institute Bioscience (QIB) and the Norfolk and Norwich University Hospital (NNUH) Neonatal Intensive Care Unit (NICU) have worked as part of a collaborative team to determine whether routine supplements of beneficial bacteria (i.e. probiotics) could enhance the bacterial composition and function of the gut microbiota and reduce NEC rates. They found a lower incidence of NEC in preterm babies given routine probiotic supplements compared with a historical cohort that did not receive probiotics and that probiotic supplementation supported establishment of a Bifidobacterium-dominated gut microbiota that increased availability of milk sugars and displaced pathogenic bacteria.

Two key research activities were involved. The first was a retrospective review of data collected on the health outcomes associated with routine probiotic use in the care of preterm babies while the second was the Baby-Associated MicroBiota of the Intestine (BAMBI) Study[iv] which evaluated the mechanisms driving the observed beneficial effects of probiotics.

The retrospective data review[v] was designed and led by Professor Paul Clarke of the NNUH NICU and the University of East Anglia (UEA), with significant contributions from Dr Lindsay Hall, Dr George Savva and Dr Claire Robertson. Its purpose was to compare the health outcomes (rates of NEC, late onset sepsis and mortality) of preterm babies admitted to NNUH NICU in the 5 years before, and the 5 years after, the introduction of routine daily administration of probiotics in January 2013.

In total, data from 982 preterm babies born between January 2008 and December 2017 were included; 469 pre-implementation babies that were not given probiotics, and 513 post-implementation babies that received probiotics. The multi-strain probiotic used was a mixture of a Lactobacillus species and a Bifidobacterium species (a second Bifidobacterium species was also administered after April 2016), and was provided daily in milk from birth until the equivalent of 34 weeks post-conception.

The BAMBI study was led by Dr Lindsay Hall and her research group (Cristina Alcon-Giner, Dr Matthew Dalby, Magdalena Kujawska, Dr Raymond Ku) working collaboratively with NNUH NICU, UEA, Imperial College London and the University of Cambridge.

Between 2013 and 2017, the project compared the gut microbiota of 101 preterm babies that had received probiotics in their milk while in the NNUH NICU, with the microbiota of 133 preterm babies in other NICUs that were not receiving routine probiotic supplementation. The babies were otherwise matched by age, sex and delivery method (cervical or caesarean section).

With parental consent, researchers collected faecal samples four times from each baby during their first 100 days of life. The composition and abundance of the bacteria in these samples, which constitute the gut microbiota, was determined using gene profiling; metabolomic analysis was also used to examine acetate and lactate levels which are indicators of milk breakdown and the release of nutrients that are then available to the baby.

“Ours is the first UK study to evaluate the potential impact of routine probiotics use on NEC and sepsis rates. It has been a big team effort to boost the gut health of these tiny vulnerable babies at the beginning of their lives and help them get the right gut bacteria from the start. We are proud to have completed this important research, which suggests that our use of probiotics has saved lives by preventing many cases of NEC and possibly sepsis too. We’re feeding more than one billion healthy live bacteria a day to each baby and it seems to have had the beneficial effect on reducing NEC that we had hoped for. Most NICU departments in the UK are still not routinely giving probiotics so we hope this research might encourage more hospitals to start giving early probiotics to protect babies.” Prof. Paul Clarke, NNUH NICU.

From the retrospective data review it was clear that rates of NEC in preterm babies were higher in the pre-implementation group (7.5%, 35 babies) than in the probiotics group (3.1%, 16 babies), independent of breast milk feeding rates. Rates of late-onset sepsis were twice as high in the pre-implementation group (22.6%, 106 babies) compared with the probiotics group (11.5%, 59 babies) and no episode of sepsis occurred due to the probiotic bacteria themselves. Mortality (all causes) rate was lower in the probiotics group (9.2%, 47 babies) than in the pre-implementation group (14.3%, 67 babies). Office for National Statistics figures report that the mortality rate of preterm and lower birth weight babies is 10-40 times higher than average[vi]. Despite this, in 2018, only 17% of UK NICU wards were routinely supplementing milk with probiotics[vii].

NEC is the most common serious intestinal disease amongst premature infants, occurring most frequently in very-low birthweight (VLBW) preterm infants weighing <1500g. Premature babies suffering from NEC can suffer an agonising death. Families suffer unimaginable trauma. Globally, NEC affects one in ten preterm babies. Every year within the UK alone, 265 infants are diagnosed with severe NEC, of which 123 succumb to this devastating disease. Globally, it has been estimated that, for every 100 VLBW infants born in a NICU, seven will develop NEC[viii]. Crucially, infants can succumb very rapidly (less than 6-8hours), which often results in emergency-surgical-intervention. NEC related surgical interventions cost the NHS ~£100k per patient, whilst prolonged-hospital-stays cost an estimated £400-500m per annum. The USA spends ~$2-3 billion per annum treating infants with NEC, yet neither survival rate nor therapy has changed in last 30years[ix]. Regardless-of-the-need for surgical intervention, physical/neurological development of NEC sufferers is compromised leading to lifelong care needs. One valid conclusion from the cumulated mass of current evidence is that widespread UK adoption of dual-strain probiotics for VLBW infants could save the lives of more than 50 babies each year, improve the health outcomes of VLBW preterm infants and reduce the huge NEC related cost burden to the NHS as a result of shorter hospital stays and a reduced number of required surgical procedures.

The retrospective data review has generated significant academic interest; the published paper [v] (July, 2020) has been downloaded over a thousand times (to date) and is already being cited. It has generated a great deal of attention on social media; with an Altmetric attention score of 112 the paper is in the top 5% of all research outputs. Of those who tweeted about the article (127 to date), 23% were from outside the UK; 58% were from the public, 24% from medical professionals, and 16% from scientists.

The BAMBI research study represents the largest and most comprehensive observational study conducted to date on the mechanisms responsible for the beneficial impact of probiotic supplementation on preterm babies. While past reviews had indicated positive benefits to infants from probiotic use, clinical trials had provided variable results, often because they were limited by low numbers of participants and/ or an absence of whole-genome sequencing data on either the probiotics used or the gut microbiota of the recipient babies. This was robustly addressed in BAMBI which enabled the team to identify clear differences in the microbiota profiles between the babies receiving probiotics and those that did not. Babies receiving probiotics had microbiota dominated by Bifidobacterium species, while those not receiving probiotics had a range of bacteria including potentially disease-causing species of Staphylococcus, Escherichia and Klebsiella. The abundance of Bifidobacterium remained high for up to 60 days after supplementation had ceased.

Differences in microbiota composition associated with probiotic use were consistent and unaffected by delivery method or whether the babies were fed their own mother’s breast milk or donor breast milk. Although all babies received breast milk, without probiotic supplementation this was insufficient to attain the levels of Bifidobacterium equivalent to those found in full-term babies. Even in extremely low birth weight infants (<1,000g) supplementation enhanced Bifidobacterium levels compared with similar babies not receiving probiotics. Therefore, even the most vulnerable of preterm babies can benefit from probiotic supplementation. The BAMBI study also showed that, while Bifidobacterium prevalence was reduced during long-term antibiotic use, when this stopped, Bifidobacterium rapidly re-established in the group receiving probiotics. Samples from those babies receiving probiotics also had smaller quantities of human breast milk sugars (specifically oligosaccharides [HMOs]) and greater quantities of the milk breakdown products acetate and lactate, indicating that milk had been broken down more effectively by babies receiving probiotics. Acetate and lactate also reduced the pH, which boosted immunity and presumably made the gut environment too acidic for many disease-causing bacteria to flourish. Together, these results are a powerful indication that probiotic supplementation improves the health of preterm babies by supporting establishment of a healthy, balanced, Bifidobacterium-dominated gut microbiota that increases HMO breakdown, displaces pathogenic bacterial species, and more closely resembles that of full-term babies.

“This study highlights the power of today´s high-throughput DNA sequencing technologies for rapidly evaluating, at high resolution, the colonisation of probiotic bacterial strains in the gut of preterm infants, and their relationship with the resident bacteria.”  Dr Cristina Alcon-Giner, the Hall Lab.

The published paper (Aug. 2020) is generating significant academic impact, with an Altmetric attention score of 115 (top 5% of all research outputs). At time of drafting it has also been mentioned in three newspaper articles, two blogs, one Facebook page and has already been Tweeted 137 times.

“Our neonatal unit is proud to have played an integral part in this major study. We’re thrilled to see the results published after many years’ hard work. While our NICU has been giving probiotics routinely to protect very preterm babies since 2013, this study gives us a much better understanding of the mechanisms by which they benefit from us putting billions of live bacteria into their immature gut daily.”  Prof. Paul Clarke, NNUH NICU.

“This work highlights how modulating the preterm gut microbiota with beneficial bacteria like Bifidobacterium can result in real improvements in health outcomes in these fragile and at-risk babies. This is one of the largest studies with preterm infants to date, and we were excited to find that matching the right probiotic Bifidobacterium – a strain that can digest breast milk – allowed it to persist in the gut and as a result significantly reduce potentially nasty bacteria that have been associated with serious infections. We hope that our findings will help direct future clinical trials and practice and help clinicians and healthcare professionals make a rational choice when it comes to diet-microbe combinations, and ultimately help these at-risk preterm babies.” Dr Lindsay Hall, QIB research lead.

As an example of how the BAMBI study has involved families, two participants in the study were twins, Benjamin and Isaac Gotts, born after only 27 weeks of gestation, weighing just 1,263g (2lb 13oz) and 1,409g (3lb 2oz). They received daily probiotics as part of their routine treatment to limit the chances of NEC. The boys were on the NNUH NICU for 77 days and during that time faecal samples were collected by the nurses and, when the twins were more stable, by their parents, for the BAMBI project. After discharge, Mrs Gotts continued to collect samples and return them to QIB for evaluation. This continued until the boys’ 3rd birthday as part of an ongoing extension of this research.

“The studies are invaluable in my opinion, the more knowledge we gain, the better. I truly hope that by simply sending in samples each month, we may have contributed to other babies not suffering from NEC. Another baby on the ward at the same time as our twins developed NEC and he had to have a large part of his bowel removed. He has a stoma bag and is now fed by liquid nutrition so we are very aware of the devastation it can cause.” Mrs Helen Gotts, mother of trial participants Benjamin and Isaac.

Photos of Benjamin and Isaac Gotts provided by their mother Mrs Helen Gotts and showing them when they were first born, and how happy they look now.

In the UK the basic cost to the NHS for a baby in neonatal intensive care is an average of £1,445 a day (2017/18 data)[x]. Probiotic administration to preterm babies has the potential to reduce the amount of time they spend in hospital, directly reducing the financial burden on NHS facilities, in addition to significantly improving infant health. While the processes leading to life threatening conditions such as NEC are complex, overgrowth by harmful pathogens is a key factor. Routine daily provision of Lactobacillus and Bifidobacterium probiotics in the NNUH NICU since 2013 proved to be a cheap (<£2 a day) and simple intervention that significantly reduced cases of NEC, the requirement for surgical interventions and late-onset sepsis. The BAMBI study indicated that probiotic supplementation supported re-establishment of a healthy gut microbiota after antibiotic treatments, reduced the occurrence of harmful pathogens and aided the digestion of milk. Furthermore, the apparent impact of reduced NEC incidence was particularly pronounced in the first 2 weeks after birth, implying that achieving early probiotic-induced stabilisation of bacteria in the gut is key to reducing mortality rates.

Read more about this research here: and

Front cover of a document produced by the World Health OrganisationUpdate December 2022

The World Health Organisation (WHO) recommendations for care of the preterm or low-birth-weight infant, published in 2022 state that “Probiotics may be considered for human-milk-fed very preterm infants (< 32 weeks’ gestation).”

The WHO document cites the published summary of this study as evidence for this statement (reference 138).

The retrospective data review was part funded by: a Wellcome Trust Investigator award to LJH (100974/C/13/Z); a BBSRC ISP grant for Gut Health and Food Safety to LJH (BB/ J004529/1); BBSRC ISP grants for Gut Microbes and Health BB/R012490/1 and its constituent project(s) (BBS/E/F/000PR10353 and BBS/E/F/000PR10355) to LJH. GMS was supported by the BBSRC Core Capability Grant BB/CCG1860/1. CR received a Bliss travel bursary sponsored by the pharmaceutical company Chiesi, which supported presentation of data from the review at a conference.

The BAMBI study was funded by a Wellcome Trust Investigator award (100974/C/13/Z) and a Biotechnology and Biological Sciences Research Council (BBSRC) Doctoral Training Grant (BB/M0112116/1) in addition to QIB Institute Strategic Programme (ISP) grants for Gut Health and Food Safety (BB/J004529/1) and Gut Microbes and Health (BB/R012490/1).

[ii] World Health Organization. 2019. Preterm birth. Accessed September 25, 2019.
[iv]Microbiota supplementation with Bifidobacterium and Lactobacillus modifies the preterm infant gut microbiota and metabolome: an observational study. C. Alcon-Giner et al. Cell Reports Medicine 1, 1000077, August 2020.
[v]Robertson C, Savva GM, Clapuci R, Jones J, Maimouni H, Brown E, Minocha A, Hall LJ, Clarke P. Incidence of necrotising enterocolitis before and after introducing routine prophylactic Lactobacillus and Bifidobacterium probiotics. Arch Dis Child Fetal Neonatal Ed. 2020 Jul;105(4):380-386.
[vii] Duffield S.D., Clarke P. Current use of probiotics to prevent necrotising enterocolitis. Arch. Dis. Child. Fetal Neonatal Ed. 2019;104:F228.
[viii]Alsaied, A., Islam, N. & Thalib, L. Global incidence of Necrotizing Enterocolitis: a systematic review and Meta-analysis. BMC Pediatr 20, 344 (2020).
[ix]Lanik, W. E., Xu, L., Luke, C. J., Hu, E. Z., Agrawal, P., Liu, V. S., Kumar, R., Bolock, A. M., Ma, C., Good, M. Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation. J. Vis. Exp. (132).
[x]NHS Archived Reference Costs

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