Normal Body Flora Flashcards
What is normal body flora?
Mixture of microbes normally found at any anatomical site in a healthy organism.
What are examples of the normal body flora?
Vast majority of normal flora are bacteria, but could be protozoa, viruses, etc.
What are the most common sites to find body flora?
Mucous Membranes
skin
What are the two types of relationships between the host and body flora?
- Temporary or Permanent
2. Optional or Obligatory
Colonization characteristics of normal body flora with host?
Some bacteria occupy more than one niche within the same host.
Some bacteria occupy only one niche: possess a tissue tropism (determined by bacterial ligand-host receptor interactions.)
Variation in types and numbers of microflora at one site.
Several combinations of microflora at same site in different hosts.
How do newborns acquire normal flora?
Foetus in utero- Free of organisms, a sterile environment.
Natural Processes-
Passing through the vagina
Surface contact with mother/dad’s skin
Suckling from a breast and swallowing
Inhalation of environmental bacteria
Direct contact with inanimate objects
Artificial methods: Probiotics
What are the three categories of factors which influence the type and numbers of normal flora at a specific site?
- Environmental Factors
- Host/Genetic Factors
- Physical activities
What are environmental factors that influence the type and numbers of normal flora at a specific site?
Availability or unavailability of oxygen (obligate aerobes/anaerobes).
The presence of appropriate receptor sites for attachment.
pH of the host site (e.g. stomach)
Nutrients; type and amounts
Effect of other microorganisms at the site.
What are Host/genetic factors that influence the type and numbers of normal flora at a specific site?
Immunological response of the host to the microbe.
Physiological state
(e.g. Pregnancy)
Age.
Genetic factors.
What are Physical activities that influence the type and numbers of normal flora at a specific site?
Use of detergents –washing and bathing
Oral and topical antibiotics
Daily oral hygiene
Sexual activity
What are benefits of normal flora?
Synthesis and excretion of vitamins.
Competitive exclusion –attach to all receptors first excluding pathogens.
Directly kill other nearby bacteria through production of bacteriocins
Stimulate the development of certain tissues
Stimulate the production of cross-reactive antibodies
Hazards of Normal Body Flora?
Bacterial synergism-allows an organism to become pathogenic when ordinarily it is not.
Opportunistic pathogens -usually occurs when host immunity is impaired, normal flora bacteria (endogenous microbes) may cause disease.
Causes primary infection in a susceptible or immunosuppressed host.
Complicates surgical wounds.
Production of carcinogens.
What are the components of Normal body flora?
Mainly bacteria
Eukaryoticfungi
Protists
Methanogenic Archaea
Characteristics of Normal body flora and tissues?
Show tissue tropism
Specialized ligands or adhesins: Capsules, Fibriae,
Cell wall components
Construct biofilms
What are the normal flora found in skin?
Bacteria:
- Staphylococcus spp. (Staphylococcus epidermidis, Staphylococcus aureus)
- Propionibacteriumacnes
- Micrococcus spp.
Yeasts
Malassezia spp.
Mites
Demodex spp.