A Gut-Friendly Powder That Didn't Stay: What a Bangladesh Study Teaches Us About Probiotics for Newborns

A plain-language look at the mSphere Bangladesh trial (Pell and colleagues) testing whether a promising probiotic-plus-prebiotic mix settles into a baby's gut

Doctors have long hoped that giving newborns a friendly bacterium in the first days of life might protect them from dangerous infections. A carefully run study in Bangladesh recently tested one such product and found that, while the bacterium showed up in babies' stool for a few weeks, it faded away and did not settle in for the long term. The result does not mean probiotics are useless, but it does overturn a key assumption about how this particular product was thought to work — and it explains why a treatment that seemed to help babies in one country may behave very differently in another.

Why doctors are interested in "good bacteria" for babies

Newborn infection, called sepsis, is one of the most serious threats to a baby's first weeks of life, and it is especially common in parts of the world with fewer medical resources. A recent study set out to understand a product that had raised real hope on this front [1]. The idea behind that product is simple and appealing. A baby's intestine is home to trillions of bacteria, and in the first days after birth this community is just getting established. The hope is that adding a carefully chosen "good" bacterium early on can crowd out harmful germs and steer the developing gut in a healthier direction, lowering the chance of a life-threatening infection later. Because such a powder is cheap and does not require special equipment, it could, in principle, save many lives where they are most at risk.

The exciting result that started it all

The product tested here combines a specific probiotic bacterium — a strain of Lactiplantibacillus plantarum — with a special sugar called fructooligosaccharide, or FOS, that is meant to feed the bacterium. This kind of "probiotic plus prebiotic" combination is called a synbiotic. It first drew attention from a large study in rural India, where more than 4,500 newborns were given either the synbiotic for seven days or a look-alike placebo, and the babies who received the synbiotic had about 40% fewer cases of sepsis and death in their first two months [2]. That was a striking result, because sepsis is such a major cause of newborn death worldwide — health researchers estimate roughly 2,200 cases for every 100,000 babies born, with the heaviest toll in lower-income countries [3]. A smaller companion study had also suggested that the bacterium took up residence in babies' guts and stayed for months. Together, these findings created a hopeful picture: a short, inexpensive course early in life that leaves behind a lasting protector.

Why scientists knew they had to check carefully

Here is where the history gets instructive. Over the years, doctors have learned that "good bacteria" are not all interchangeable, and that a product that helps in one situation may do nothing in another. In one large British study called the Probiotics in Preterm infantS (PiPS) trial, carried out across 24 hospitals in the south of England, a different probiotic given to very premature babies did not reduce infection, serious bowel disease, or death [4]. In another large study in Australia and New Zealand — the ProPrems trial, which tested a three-strain probiotic mixture in very premature babies — the product reduced a dangerous bowel condition but not bloodstream infection [5]. When researchers pool many such studies together, probiotics do appear to help prevent that bowel disease and lower deaths in the most premature babies, but the benefit depends heavily on exactly which product is used [6]. For this reason, expert groups such as the American Academy of Pediatrics urge caution and remind clinicians that these products are not officially approved as medicines and that each one must be judged on its own evidence [7]. So before anyone could recommend the Indian synbiotic more widely, it was essential to test whether it behaves the same way in a new place.

What the Bangladesh study actually did

The new study took place at two public hospitals in Dhaka, Bangladesh, and involved 519 newborns who weighed at least 1,500 grams and were feeding by mouth in their first few days [1]. The babies were randomly divided into five groups. One group received a placebo. The others received the same bacterium used in India, given either as a single dose or once a day for seven days, and either with or without the FOS sugar. "Randomly divided" means a computer, not the doctors or parents, decided which baby got what, and neither the families nor the staff knew which product any baby received until the study ended — a design that keeps the comparison fair.

Instead of trying to count infections, which would have required tens of thousands of babies, the researchers asked a more basic and answerable question: does the bacterium actually settle into the baby's gut? To find out, they collected stool samples over the first two months and used a precise laboratory test that could detect the exact strain they had given — distinguishing it from the many other, naturally present bacteria that look similar. This let them track, week by week, whether the added bacterium was building up and staying, or simply passing through.

The key finding: it showed up, then it left

The bacterium did appear, and the more the babies received, the more of it showed up at first. In the group that got seven days of the bacterium plus FOS, the strain was detectable in about 62% of stool samples in the two-month window, compared with only 4% in the placebo group [1]. But the crucial detail is what happened over time. The amount of bacterium peaked just one to two days after the first dose and then steadily declined — no matter whether a baby had received a single dose or a full week of doses. By around two months of age, the babies who had received the bacterium were no different from those who had received placebo. In everyday terms, the "good" bacterium behaved like a visitor passing through rather than a resident moving in. That was the opposite of what the earlier findings had led scientists to expect, and it means the assumption that a short course leaves behind a lasting protector did not hold true in these babies.

Two other results are worth knowing. First, adding the FOS sugar or giving more doses did not help the bacterium stick around longer, which matters because leaving the sugar out would make the product cheaper to use on a large scale. Second, the product was safe: it was easy to give, caused no more tummy troubles than the placebo, and did not cause any infections itself. So the disappointment here is not about safety — it is about whether the bacterium does what everyone assumed.

Why the same product behaved so differently in two countries

The natural question is why a bacterium that seemed to persist in rural India would fade in urban Bangladesh. The likely answer lies in how a baby's gut community forms. In the first year of life, the mix of bacteria in a baby's intestine changes constantly and is shaped by how the baby was born, how it is fed, whether it received antibiotics, and the surrounding environment [8]. The Bangladeshi babies differed from the Indian babies in several of these ways — for example, far more were born by Caesarean section and nearly all of their mothers had received antibiotics around delivery — and any of these differences could make it harder for a newcomer bacterium to find a foothold. Importantly, scientists know that lasting colonization is possible when the bacterium and its food source are well matched: a different probiotic, a strain of Bifidobacterium, has been shown to settle stably in breastfed babies and reshape their gut [9], and follow-up studies found it could still be detected a full year later [10]. The lesson is that whether a "good" bacterium takes root depends on a good match between the bacterium, its food, and the gut it is entering — a match that worked in one case but not in this one.

What this means for families, and what comes next

If your baby is in a nursery that uses or is considering probiotics, this study is a reason for thoughtful questions rather than alarm. Its most honest message is that we still do not know whether this particular synbiotic prevents infection in babies like those in Bangladesh — the study was not designed to answer that — but we now know that it does not stay in the gut the way people assumed [1]. That is genuinely useful, because it tells researchers they cannot simply borrow a product from one place and expect it to behave identically somewhere else, and it hints that any protection the product offers might come from a brief effect during the days it is given rather than from a permanent new resident. What researchers are working on next is a larger, more definitive trial in the right population, testing whether longer courses that cover the whole risky early period can actually reduce infections, and whether the FOS sugar is needed at all. For now, the takeaway for families is reassuring in one respect and humbling in another: these products appear safe, but proving that a specific one truly protects a specific group of babies takes exactly the kind of careful, honest testing this study represents. Families interested in related questions about probiotics and a serious newborn bowel disease can read In[Neo]Sight's companion article (https://inneosight.org/en-US/articles/probioticsnec-nma-2025).

References

  1. Pell LG, Qamar H, Bassani DG, et al. Neonatal administration of Lactiplantibacillus plantarum ATCC 202195 with or without fructooligosaccharide in Bangladesh: a placebo-controlled randomized trial. mSphere. 2025;10(3):e01032-24. doi:10.1128/msphere.01032-24 ↩
  2. Panigrahi P, Parida S, Nanda NC, et al. A randomized synbiotic trial to prevent sepsis among infants in rural India. Nature. 2017;548(7668):407-412. doi:10.1038/nature23480 ↩
  3. Fleischmann-Struzek C, Goldfarb DM, Schlattmann P, et al. The global burden of paediatric and neonatal sepsis: a systematic review. Lancet Respir Med. 2018;6(3):223-230. doi:10.1016/S2213-2600(18)30063-830063-8) ↩
  4. Costeloe K, Hardy P, Juszczak E, et al. Bifidobacterium breve BBG-001 in very preterm infants: a randomised controlled phase 3 trial. Lancet. 2016;387(10019):649-660. doi:10.1016/S0140-6736(15)01027-201027-2) ↩
  5. Jacobs SE, Tobin JM, Opie GF, et al. Probiotic effects on late-onset sepsis in very preterm infants: a randomized controlled trial. Pediatrics. 2013;132(6):1055-1062. doi:10.1542/peds.2013-1339 ↩
  6. Sharif S, Meader N, Oddie SJ, et al. Probiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants. Cochrane Database Syst Rev. 2023;(7):CD005496. doi:10.1002/14651858.CD005496.pub6 ↩
  7. Poindexter B; Committee on Fetus and Newborn. Use of probiotics in preterm infants. Pediatrics. 2021;147(6):e2021051485. doi:10.1542/peds.2021-051485 ↩
  8. Bäckhed F, Roswall J, Peng Y, et al. Dynamics and stabilization of the human gut microbiome during the first year of life. Cell Host Microbe. 2015;17(5):690-703. doi:10.1016/j.chom.2015.04.004 ↩
  9. Frese SA, Hutton AA, Contreras LN, et al. Persistence of supplemented Bifidobacterium longum subsp. infantis EVC001 in breastfed infants. mSphere. 2017;2(6):e00501-17. doi:10.1128/mSphere.00501-17 ↩
  10. O'Brien CE, Meier AK, Cernioglo K, et al. Early probiotic supplementation with B. infantis in breastfed infants leads to persistent colonization at 1 year. Pediatr Res. 2021;89(7):1757-1764. doi:10.1038/s41390-020-01350-0 ↩