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.
What are the normal flora within the conjunctivae?
1.Staphylococcus spp. (Staphylococcus epidermidis Staphylococcus aureus) 2.Propionibacteriumacnes 3.Streptococcus spp. 4..Haemophilus sp.
What are the normal flora within the upper respiratory tract?
- Staphylococcus spp.(Staphylococcus epidermidis Staphylococcus aureus)
- Corynebacterium spp.
- Streptococcus spp.(Streptococcus pneumonaie Streptococcus pyogenes)
- Haemophilus influenza
- Neisseria meningitides
What are the normal flora within the oral cavity?
Streptococcus spp.(Streptococcuss alivarius (until teeth appear), Streptococcus mutans, Streptococcus sanguis, Staphylococcus spp.
Bacteroides spp.
Diphtheroids (nonpathogenic Corynebacterium spp.)
Lactobacillus spp.
What are the normal flora within the lower intestinal tract?
Lactobacillus spp.
Enterococcus spp - Enterococcusfaecalis
Escherichia coli
Bacteriodes spp.
What are the normal flora within the large intestine?
Bacteria present here are qualitatively similar to that found in faeces
Bacteriodes spp.
Lactobacillus spp.
Bifidobacterium spp.
Clostridium spp. -Clostridium perfringens, Clostridium septicum
Enterobacteriaceae:
E. coli, Klebsiella, Enterobacter, Pseudomonas aeruginosa, Proteus mirabilis
Methanogens
What are the normal flora within the urogenital tract?
Sterile
Urinary tract flushes every few hours
What are the normal flora within the urethra?
Staphylococcus spp. (Staphylococcus epidermidis, Staphylococcus aureus
Streptococcus spp.
Enterococcusfaecalis
E. coli
Proteus spp.
Corynebacterium spp.
What are the normal flora within the vagina?
Corynebacterium spp.
Staphylococcus spp.
Streptococcus spp.
Lactobacillus spp. E. coli
Yeasts: Candida albicans
What are the bacteria found within milk?
Micrococci Staphylococci Streptococci Mycoplasmas Corynebacterium bovis
How are rumen bacteria classified?
According to function:
1. Fibre-digesting or Cellulolyticbacteria
2.Starch and Sugar-Digesting (or Amylolytic) bacteria
What are the rumen bacteria classified according to Fibre-digesting
Ruminococcus flavefacians
Ruminococcus albus
Bacteriodes succinogenes
Butyrivibriofibrisolvens
What are the rumen bacteria classified according to Starch and Sugar-Digesting bacteria?
Bacteriodes ruminocola
Bacteriodes amylophilus
Selenomonas ruminantium
Streptococcus bovis Succinomonas amylolytica
What are probiotics?
Oral administration of living organisms to promote health
Competitive exclusion agents, e.g. Bifidobacterium spp.and Lactobacillus acidophilus
Mechanism speculative: competition with other bacteria; stimulation of nonspecific immunity
Species specific: adherence and growth (tropism)
What are prebiotics?
Non-digestible food that stimulates growth or activity of GI microbiota, especially bifidobacteriaand lactobacillus bacteria (both of which are non-inflammatory)
Typically a carbohydrate: soluble fiber
What is the effect of antimicrobials on normal flora?
Antibiotic overuse or misuse –growth promoters in farm animal production.
Normal flora may be vehicles of drug resistance traits,
De-stabilize the bacteria-host balance.
Antibiotic-associated diarrhoea, e.g. Candida spp
Pseudomembranous colitis –toxic megacolon
