ABSTRACT
This review details the success of different probiotic agents to provide protection in the host from infection by pathogenic microbial agents. Probiotics are bacteria that interfere and kill pathogens but the mechanisms employed by these agents in preventing infection and disease vary from host to host. In this review the use of probiotics in evolutionary distinct hosts are discussed. The early discovery of antibiotics (such as penicillin and streptomycin) and newer generation drugs have played and continue to play vital roles in controlling infections by pathogenic agents. The extensive and indiscriminate uses of antibiotics have contributed to the survival of resistant microbial agents that cannot be controlled by conventional antibiotics. The resistant strains damage cells, tissues and organs resulting in injury and or death to the host. Probiotic agents block sites pathogenic agents need for adherence to surfaces and simultaneously activates innate and adaptive components of the immune system. The multipronged attack by probiotics are more efficient than just relying on antibiotics to disrupt cell wall structures and or poison metabolic pathways in pathogenic agents.