Abstract: The combination of specific immunoglobulins plus activated Bifidobacteria strains or other beneficial bacteria is described with the designed efficacy to colonize unstable microbiome communities in humans or other animals, restoring the keystone Bifidobacteria strains or other beneficial bacteria to compositional and functional importance in the intestine and improve overall health and reduce pathogenic infections in the host. Secretory immunoglobulin A (SIgA), when bound via specific glycans to select commensal bacteria grown on human milk oligosaccharides (HMOs), enhances the colonization potential of commensals through protection from intestinal digestion, enhancing attachment, and dampening host immune response.