Iron deficiency anaemia (IDA) is closely associated with the gut microbiome, as microbial composition influences iron bioavailability. Small intestinal bacterial overgrowth (SIBO), a form of dysbiosis, may interfere with anaemia treatment, yet it has not been investigated as a direct consequence of iron deficiency. This study aimed to characterize the small intestinal dysbiosis linked to IDA and to identify microbial patterns indicative of SIBO. An animal model of IDA was employed to analyse the microbiome of the small intestine, focusing on community structure and functional properties. Anaemia was confirmed using haematological and biochemical markers. Microbiome profiling was conducted through 16S rRNA gene sequencing. In addition, bacterial load was quantified by 16S rRNA qPCR. qPCR confirmed a significantly elevated bacterial load across all three regions of the small intestine during anaemia, reaching levels compatible with SIBO. A progressive increase was observed in alpha diversity from the jejunum to the ileum during IDA. Taxonomic analysis revealed enrichment of fermentative and colonic-associated species, including Clostridium, Escherichia-Shigella and Lactobacillus. Lastly, functional predictions indicated increased activity in pathways related to carbohydrate fermentation and gas production—metabolic signatures typically linked to SIBO. Iron deficiency was found to induce marked taxonomic and functional alterations in the small intestinal microbiome, especially in distal regions, accompanied by an increased bacterial load. These findings support the concept that iron deficiency promotes microbial shifts characteristic of SIBO, suggesting that iron deficiency may act as a predisposing factor in its pathogenesis.
Soriano-Lerma et al. (2026) studied this question.