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Flashcards in 10 - Normal Microbiota Deck (18):
1

Mutualism definition

Both organisms benefit from symbiosis

2

Neutralism definition

Neither organism derives benefit or harm

3

Commensalism definition

One organism benefits, the other derives neither benefit nor harm

4

Parasitism definition

One organism benefits at the expense of the other

5

Do sterile sites have normal flora?

No

6

Mechanisms of formation of sterile sites

Surface cleaning - lungs

Barriers with uni-directional flow - urinary tract

Sterility maintained by physical separation - spinal cord

7

Tissue tropism definition

Propensity for a particular to grow in a particular habitat

8

Physical variables affecting bacterial growth

Moisture
Temperature
pH
O2 availability
Nature of surface

9

Bacteria on skin

Staph. epidermis
Staph. aureus (mainly nasal)

Propionibacterium acnes

Note: bacteria near orifice similar to bacteria in orifice

10

Nasopharyngeal flora

Staph. aureus
Haemophilus influenzae
Strep. pneumoniae
Neisseria meningitidis
Staph. pyogenes

11

Vaginal flora

prepubescent - skin flora, low GI flora, mainly E.Coli

post-puberty - glycogen produced due to circulating oestrogens. E.g. lactobacillus acidophilis, ferment glycogen. Skin flora. A few C.albicans

12

GI tract - stomach + small intestine - bacteria present

Acid-tolerant lactobacilli
Helicobacter pylori

13

GI tract - large intestine

95-99% anaerobes

Aerobic bacteria - enteric gram--ve bacilli

e.g. E.Coli

14

Benefits of normal flora

Synthesis and excretion of vitamins - K&B12

Colonisation resistance - environment manipulation e.g. pH; antibacterial agents

Induction of cross-reactive antibodies

15

C.diff infections

Hospital acquired infection usually >60 years

Main risk factor being antibiotic treatment

Destroys layers of bacteria allows C.diff invasion

16

Pathology of normal flora causes

Overgrowth - thrush
Translocation - wrong site has wrong bacteria
Cross-infection

17

Clinical conditions caused by normal flora

Abscesses
Dental caries, peridontal disease, pharyngitis
Pneumonia
Endocarditis
GI-itis, peritonitis
Urogenital infections

18

Main problem with working with normal flora

only 1% is culturable