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EMS - Mechanisms of disease > Normal microbiota > Flashcards

Flashcards in Normal microbiota Deck (13):
1

Define mutualism.

Both organisms benefit from symbiosis

2

Define neutralism.

Neither organism benefits from symbiosis.

3

Define commensalism.

One organism benefits, the other derives neither benefit nor harm.

4

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

5

Give examples of sterile sites where sterility is maintained by barriers.

Upper genital tract

Urinary tract

Middle ear

6

Give examples of sterile sites where sterility in maintained by physical barriers

Pleural cavity

Peritoneal cavity

Spinal cord

Meninges.

7

Give an example of skin flora.

Staph epidermidis. Staph aureus.

8

Give examples of nasopharyngeal commensals.

Streptococcus pyogenes (group A)

Haemophilus influenzae

Streptococcus pneumoniae

Neisseria meningitidis 7-34% in UK university students1

S. aureus

9

Why does vaginal flora change post-puberty?

Glycogen produced due to circulating antigens.
- Introduction of lactobacillus.

10

Give examples of aerobic GI bacteria?

Escherichia coli

Klebsiella spp

Enterobacter spp

Proteus spp

Citrobacter spp. etc.

11

Give examples of anaerobic GI bacteria?

Bacteroides spp., Clostridium spp. Bifidobacteria spp

12

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

13

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