Entry 7
Probiotic science page
Uses antimicrobial compounds and gut motility modulation to reduce infant colic crying time, with RCT and meta-analysis support.
Overview
L. reuteri DSM 17938 is a daughter strain of ATCC 55730. It was created by removing two plasmids that carried tetracycline and lincosamide resistance genes. This eliminated transferable antibiotic resistance concerns [1]. Direct comparison of parent and daughter strains confirmed that probiotic properties were retained. This was shown in lab tests and a human clinical trial [1]. In 2020, L. reuteri was reclassified to the genus Limosilactobacillus [6].
Mechanism
DSM 17938 produces reuterin (3-hydroxypropionaldehyde). Reuterin is a broad-spectrum antimicrobial compound made from glycerol fermentation. It is active against both Gram-positive and Gram-negative gut pathogens [1]. The strain sticks to intestinal mucus and cells lining the gut. This lets it block harmful bacteria by taking up space [1]. In living organisms, DSM 17938 changes gut microbiota composition. It also turns down pro-inflammatory cytokine pathways. This has been shown in infant and animal models [2][5]. An evolved variant, DSM 32846, keeps these functional properties. It also survives better in the gastrointestinal tract and handles stress more effectively [5].
Health Benefits
A meta-analysis (pools results from multiple trials) of randomized controlled trials showed that DSM 17938 reduces crying and fussing time in breastfed infants with infantile colic (systematic review/meta-analysis of RCTs; moderate-certainty evidence) [2]. A separate systematic review found that taking it for up to 21 days reduced antibiotic-associated diarrhoea risk in children (RR 0.50, 95% CI 0.33–0.75; RCT; moderate-certainty evidence). Shorter regimens of 14 days or less showed no effect [3]. An RCT in Thai children with acute gastroenteritis found no reduction in stool frequency or illness duration versus placebo (RCT) [4]. A long-term follow-up RCT suggested prevention of functional abdominal pain disorders in children (RCT with extended follow-up) [7]. Evidence is strongest for infantile colic in breastfed infants. Other pediatric indications remain inconclusive or limited by differences between studies.
Biology
L. reuteri (old name: Lactobacillus reuteri; new name: Limosilactobacillus reuteri) is a Gram-positive, rod-shaped bacterium. It produces lactic acid plus other byproducts from sugar fermentation. It ferments hexoses and pentoses to lactic acid, acetic acid, ethanol, and CO₂. The species colonizes the gastrointestinal tract of humans and other vertebrates [1]. DSM 17938 was derived from ATCC 55730. That strain was originally isolated from human breast milk and the GI tract [1]. Zheng et al. (2020) reclassified L. reuteri from Lactobacillus to Limosilactobacillus based on whole-genome phylogenetic analysis [6].
Bibliography
Rosander A, Connolly E, Roos S. (2008). Removal of antibiotic resistance gene-carrying plasmids from Lactobacillus reuteri ATCC 55730 and characterization of the resulting daughter strain, L. reuteri DSM 17938. Appl Environ Microbiol. 74(19):6032-6040. PMID: 18689509
Bianchi M, et al. (2026). Efficacy of Lactobacillus reuteri DSM 17938 in preterm newborns and infants with colic: a systematic review and meta-analysis of randomized controlled trials. Nutrition. 151:113327. PMID: 42485904
Szajewska H, Kołodziej M, Zalewski BM, Dinleyici EC, Łukasik J. (2026). Systematic review: Limosilactobacillus reuteri DSM 17938 for preventing antibiotic-associated diarrhoea in children. J Pediatr Gastroenterol Nutr. 82(3):781-789. PMID: 41486369
Rerksuppaphol L, Rerksuppaphol S. (2025). Efficacy of Lactobacillus reuteri DSM 17938 in Thai children with acute gastroenteritis and normal or mild dehydration in an outpatient setting: a randomized controlled trial. J Trop Pediatr. 71(4). PMID: 40618229
Ermann Lundberg L, et al. (2025). Selection, characterisation and safety of Limosilactobacillus reuteri DSM 32846, an evolved version of DSM 17938. Benef Microbes. 17(4):413-430. PMID: 41067711
Zheng J, et al. (2020). A taxonomic note on the genus Lactobacillus: Description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae. Int J Syst Evol Microbiol. 70(4):2782-2858. PMID: 32293557
Indrio F, et al. (2026). Long-Term Efficacy of Limosilactobacillus reuteri DSM17938 in the Prevention of Functional Abdominal Pain Disorders. Nutrients. 18(4). PMID: 41754204
Available Products
DSM 17938 is sold by BioGaia AB (Stockholm, Sweden). It comes as oil-based drops (Protectis) and chewable tablets for children and adults [1]. The strain is also added to young child formula products with GOS [5]. DSM 32846, an evolved version, has been described as a next-generation formulation with improved survival [5].