AbstractBacterial microbiota play a critical role in mediating local and systemic immunity, and shifts in these microbial communities have been linked to impaired outcomes in critical illness. Emerging data indicate that other intestinal organisms, including bacteriophages, viruses of eukaryotes, fungi, and protozoa, are closely interlinked with the bacterial microbiota and their host, yet their collective role during antibiotic perturbation and critical illness remains to be elucidated. Here, multi-omics factor analysis (MOFA), a novel computational strategy to systematically integrate viral, fungal and bacterial sequence data, we describe the functional impact of exposure to broad-spectrum antibiotics in healthy volunteers and critically ill patients. We observe that a loss of the anaerobic intestinal environment is directly correlated with an overgrowth of aerobic pathobionts and their corresponding bacteriophages, as well as an absolute enrichment of opportunistic yeasts capable of causing invasive disease. These findings further illustrate the complexity of transkingdom interactions within the intestinal environment, and show that modulation of the bacterial component of the microbiome has implications extending beyond this kingdom alone.