Competitive Exclusion

All organisms exist in competition for available resources.   Those that create a competitive advantage will flourish at the expense of the less competitive.

Bacteria require semi-specific environmental conditions for sufficient attachment, colonization and pathogenesis in animals. Normal commensal bacterial populations can exclude (outcompete) pathogens such as salmonella from enteric colonization though physical and chemical competition.

Enteric colonization by pathogens often requires some change in this homeostasis of normal gut floral. This change can be induced by things such as: rapid change in feed, altering the animal environment, antibiotic use, large doses of virulent bacteria, and concurrent epithelial damage by another pathogen.

Research has shown that the population of bacteria in the gut can be altered through intentional inoculation of beneficial bacteria or competitive exclusion. This practice of competitive exclusion is attempted by inoculation of animals with nonpathogenic strains of bacteria before and after apparent colonization by pathogens such as salmonella. For example, organisms such as lactobacillus produce acid substances reducing the pH and limiting the ability of non-acidophilic bacterial growth. However, the continuous maintenance of beneficial bacteria is difficult.
The maintenance of a ‘’normal” population of bacteria in the intestines of animals should be actively managed by agricultural producers as well as veterinarians.

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