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Organisms
of normal flora play an important role in the development of immunologic
competence. Animals delivered and raised under completely aseptic conditions
have a poorly developed reticuloendothelial system, low serum level of
immunoglobulin and none of the antibodies to normal floral antigen that often
cross-react with those of pathogenic organisms and confer a degree of
protection against them. Exclusionary Effects
The
normal flora produces conditions that tend to block the establishment of
e4xtraneous pathogens and their ability to infect the host. The bifidobacteria
in the colon of the breastfed infant produce an environment inimical to
colonization by enteric pathogens, this protective effect is aided by ingested maternal
IgA. Breastfeeding has clearly shown to help to protect infant from enteric
bacterial infections.
Production of Essential Nutrients by Normal flora
In
humans, member of the vitamin B group and vitamin K are produced by normal
flora. Bacterial vitamin production is reduced during broad spectrum antibiotic
therapy, and supplementation with vitamin B complex is indicated in
malnourished individuals.