[Study on the characteristics and differences of intestinal microbiota in children with allergic diseases]

Objective: Based on metagenomic sequencing technology, this study aims to investigate the characteristics and differences of the intestinal microbiota in children with different allergic diseases, providing a theoretical basis for the early prevention and treatment of allergic diseases. Methods: The study adopted a case-control research method. 214 children with allergic diseases (Group A) who visited the Suzhou Hospital Affiliated to Nanjing Medical University from March 2023 to June 2024 were selected. According to age matching, 93 healthy controls (Group H) who participated in physical examinations during the same period were also included. Fecal samples and clinical data of the subjects were collected. The subjects were grouped according to age and type of allergic disease, and the fecal samples of the subjects were analyzed using metagenomic sequencing technology to study the characteristics and differences of the gut microbiota in different groups. The subjects were divided into 0-1 year old group (A1 and H1), 1-3 year old group (A2 and H2), and≥3 year old group (A3). According to the disease type, A1 was divided into food allergy without atopic dermatitis (F1) group and food allergy with atopic dermatitis (F2) group, A2 was divided into atopic dermatitis (AD) group, allergic rhinitis (AR) group and AD with AR group. A3 was divided into AR group, AD with AR group and AR with asthma (AS) group. Results: With age increase, the number of species annotated at the genus level in the microbiota showed a gradually increasing trend. There were significant differences in the diversity and composition of the intestinal microbiota between the allergic disease group and the control group. In the diversity analysis, it was found that there were differences in species richness between group A and group H (chao index, group A: 955.2±226.1, group H: 762.3±260.9, W=5 664, P<0.000 1), and significant differences in β-diversity between group A2 and group H2, and between group A3 and group AD-AR and group AR-AS (R=0.045, P=0.018, R=0.044, P=0.011). At the species level, the allergic disease group was mainly enriched with Bifidobacterium, Enterococcus, Escherichia, Mediterraneibacter and Blautia, while the control group was mainly enriched with Bifidobacterium. By age group analysis, the relative abundance of Mediterraneibacter and Blautia in group A1 (0-1 years old) was significantly higher than that in group H1 (Mediterraneibacter: A1: 5.2±9.4, H1: 0.9±2.1, W=718, P=0.000 8; Blautia: A1: 3.5±6.0, H1: 1.3±3.2, W=701, P= 0.000 5). In group A2 (1-3 years old), the relative abundance of Bacteroides and Faecalibacterium was significantly higher than that in group H2 (Bacteroides: A2: 5.6±8.7, H2: 3.1±5.8, W=456, P=0.020 8; Faecalibacterium: A2: 2.6±2.8, H2: 1.2±1.9, W=395, P=0.002 8). In the clinical subtype analysis, the relative abundance of Blautia and Fusicatenibacter was significantly increased in AR children (Blautia: AD: 8.0±7.9, AD-AR: 13.5±8.3, AR: 20.2±7.8, H=9.300 8, P=0.009 6; Fusicatenibacter: AD: 0.5±0.9, AD-AR: 1.2±1.6, AR: 2.2±2.4, H=7.878 3, P=0.019 5), and the relative abundance of Escherichia was significantly increased in AD children (AD: 3.3±4.3, AD-AR: 1.8±4.5, AR: 0.8±2.0, H=9.476 6, P=0.008 8). In group A3 (≥3 years old), Mediterraneibacter was significantly enriched (A3: 6.3±6.9, H3: 2.9±1.9, W=571, P=0.039 7), and the relative abundance of Anaerostipes was significantly increased in AR children (AD-AR: 2.9±2.9, AR: 5.2±4.9, AR-AS: 3.2±3.5, H=7.269, P=0.026 4). Conclusion: In infancy, the species of intestinal flora gradually increase with age. There are significant differences in the composition of intestinal flora among children with different allergic diseases. Bifidobacterium, as the main dominant species in infancy, has a lower relative abundance in the allergic disease group at different ages than in the healthy control group, suggesting that the lack of Bifidobacterium may be related to the occurrence and development of allergic diseases.