Temporal Shifts in Gut Microbiota and Host Immunity During Chronic Diarrhea in an Infant Rhesus Macaque: A Longitudinal Case Study Based on Multi‐Omics

Diarrhea remains a major health challenge in captive rhesus macaques (RMs; Macaca mulatta), particularly among infants, yet the dynamic interplay between gut microbiota and host immune responses during disease progression remains poorly understood. Here, we conducted a longitudinal multi-omics study on a captive infant RM, analyzing 25 fecal metagenomes and 18 blood transcriptomes across diarrheal, antibiotic treatment, and recovery phases. Our results demonstrated that disease state was the primary driver of gut microbiota variation. The diarrheal phase was characterized by a significant reduction in microbial α-diversity and marked expansion of multidrug-resistant Enterobacteriaceae, including Escherichia, Shigella, and Salmonella, accompanied by severe depletion of probiotic genera such as Lactobacillus and Bifidobacterium. Correspondingly, antibiotic resistance genes targeting fluoroquinolones and cephalosporins accumulated substantially during diarrhea, explaining the limited efficacy of empirical antibiotic therapy. Blood transcriptome analysis revealed heightened innate immune activation, evidenced by upregulation of interferon-related genes, alongside suppression of adaptive immune pathways including interleukin-5 signaling. Integrated correlation analysis uncovered synchronized host-microbiome interactions, with inflammatory gene expression positively associated with opportunistic pathogens and negatively correlated with beneficial commensals. Clinical recovery coincided with re-establishment of probiotic populations, reduction in resistance gene burden, and normalization of immune function. These findings demonstrate that infant macaque diarrhea profoundly disrupts both gut microbial ecology and systemic immunity, supporting management strategies that prioritize targeted antimicrobial intervention and microbiome restoration over prolonged empirical antibiotic use in captive primates.