Normal microbiota Flashcards
Define mutualism.
Both organisms benefit from symbiosis
Define neutralism.
Neither organism benefits from symbiosis.
Define commensalism.
One organism benefits, the other derives neither benefit nor harm.
How are sterile body sites kept so?
Sterility maintained by barriers that allow uni-directional flow adjacent to non-sterile sites
Sterility maintained by physical separation from non-sterile sites
Closed cavities
e.g. respiratory tract
Give examples of sterile sites where sterility is maintained by barriers.
Upper genital tract
Urinary tract
Middle ear
Give examples of sterile sites where sterility in maintained by physical barriers
Pleural cavity
Peritoneal cavity
Spinal cord
Meninges.
Give an example of skin flora.
Staph epidermidis. Staph aureus.
Give examples of nasopharyngeal commensals.
Streptococcus pyogenes (group A)
Haemophilus influenzae
Streptococcus pneumoniae
Neisseria meningitidis 7-34% in UK university students1
S. aureus
Why does vaginal flora change post-puberty?
Glycogen produced due to circulating antigens.
- Introduction of lactobacillus.
Give examples of aerobic GI bacteria?
Escherichia coli
Klebsiella spp
Enterobacter spp
Proteus spp
Citrobacter spp. etc.
Give examples of anaerobic GI bacteria?
Bacteroides spp., Clostridium spp. Bifidobacteria spp
What are the benefits of normal flora?
Synthesis and excretion of vitamins
- e.g. vitamins K and B12 secreted by enteric bacteria
Colonisation resistance
Environmental manipulation
- e.g. pH
Antibacterial agents
- e.g. colicins, bacteriocins, fatty acids, metabolic waste products
Induction of cross-reactive antibodies
May have a protective effect
What are possible pathologies of normal flora?
Overgrowth (thrush) - excessive growth at normal site
Translocation - conjunctivitis, presence at the wrong site, spread from one surface to another, inoculation into a normally sterile site
Cross-infection - MRSA
