Neonatal Meconium Microbiota and Its Possible Association with Allergy in Two-Year Follow-up: A Pilot Study

This study aimed to investigate microbiota diversity in the first faecal (meconium) samples of newborns and to examine their possible relationship with the development of allergy over time. Considering the effects of the microbiota on immune tolerance development, the gut-brain axis, and systemic immunity, it was evaluated whether early differences in diversity and composition would be determinants of allergy risk. To overcome the limitations of traditional culturing methods, Next-Generation Sequencing (NGS) is a high-throughput method used in microbiota research. This technology enables the elucidation of the complex structure of the intestinal ecosystem and the presence of difficult-to-culture microorganisms. In our study, the composition, diversity, and structure of the human intestinal microbiota were examined in detail by metagenome analysis of the V3-V4 regions of the 16S ribosomal RNA (rRNA) gene in 10 different faecal meconium samples. Bioinformatics analyses were performed using QIIME2, and alpha-diversity (Shannon, Chao1) and beta-diversity (Bray-Curtis, UniFrac) indices were calculated. The findings confirmed that the dominant phyla were Firmicutes and Bacteroidetes. In a case in which food allergy was detected after the introduction of complementary feeding, microbial diversity in meconium was lower than in other samples, and Diaphorobacter/Clostridioides ratios were higher than in other samples. Alpha diversity indices were lower in the individual who developed allergies. Beta-diversity analyses showed that the allergic individual clustered differently from the others. Our findings indicate that the gut microbiota in early life may contain essential biomarkers for the development of allergic diseases. Current literature suggests that the gut microbiota, which develops early in life, plays a critical role in immune system development, and that disruption of this balance (dysbiosis) may be an essential factor in the pathogenesis of allergic diseases. In this context, our study aims to contribute to the body of knowledge in this field by compiling current findings on how neonatal microbiota structure affects allergic predisposition.