9. Normal Microbiota Flashcards

1
Q

which areas of skin harbour more organisms?

A

moist, protected areas of skin, eg. armpits, groin or between the toes

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2
Q

in which parts of the body is organism density the greatest?

A

oral cavities and colon

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3
Q

what are normal flora?

A

organisms found in a given location in a state of health

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4
Q

what is colonisation?

A

establishment at a site in the body

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5
Q

what is symbiosis?

A

2 or more organisms co-exist in close physical association

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6
Q

what is mutualism?

A

both organisms benefit from the symbiosis

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7
Q

what is neutralism?

A

neither organism derives benefit or harm from the symbiosis

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8
Q

what is commensalism?

A

one organism benefits, the other one neither benefits nor is harmed

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9
Q

what is parasitism?

A

one organism (parasite) benefits at the expense of the other (host)

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10
Q

what are non sterile sites?

A

sites with normal flora, are exposed to the environment either directly or indirectly, and have no mechanism in place to maintain sterility

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11
Q

what are sterile sites?

A

those with no normal flora

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12
Q

when do humans acquire flora?

A

at birth

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13
Q

what are the 3 types of sterile sites?

A
  1. sterility maintained by surface cleaning
  2. sterility maintained by barriers that allow unidirectional flow
  3. sterility maintained by physical separation from non sterile sites
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14
Q

where is sterility maintained by surface cleaning?

A

those places that are open to the environment

efficient cleaning by ciliated epithelium, removal of bacteria by coughing, sneezing or swallowing

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15
Q

where is sterility maintained by barriers that allow unidirectional flow?

A

adjacent to non sterile sites eg. cervix and upper genital tract, urethra before urinary tract

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16
Q

where is sterility maintained by physical separation from non sterile sites?

A

close cavities eg. plural and peritoneal cavities, meninges

17
Q

what factors influence what organisms colonise in which areas?

A
moisture
temperature 
pH
oxygen availability
nature of surface
18
Q

skin flora

A

coagulase -ve staph. eg. staph epidermis
staph aureus
propionibacterium acnes
the bacterium on the skin near any body orifice may be similar to those in the orifice

19
Q

mouth flora

A

viridian’s/oral streptococci

anaerobes

20
Q

what is the benefit of colonising in the mouth?

A

gain of nutrients, also provide the host with essential vitamins, synthesises by bacterial species
established normal flora can prevent colonisation of pathogenic flora

21
Q

nasopharyngeal flora - nostrils

A

skin flora

Staph aureus

22
Q

nasopharyngeal flora - pharynx

A
step. pyogenes
haemophilus influenzae
step. pneumoniae
Neisseria meningitidis
S. aureus
23
Q

vaginal flora - pre-puberty

A

skin flora

lowe GI flora, mainly E. coli

24
Q

vaginal flora, prost puberty

A

lactobacillus acidophilus
skin flora
C. albicans

25
Q

why is there a difference in flora in the vagina pre and post puberty?

A

circulating oestrogen at puberty stimulates production of glycogen in the vagina. lactobacillus acidophilus ferment the glycogen and maintain a oH of 3, preventing overgrowth of other species

26
Q

GI tract - stomach and small intestine flora

A

acid tolerant lactobacilli, H. pylori

due to inhibition of bacterial growth by low pH. predominantly aerobic becteria

27
Q

Gi tract flora - large intestine

A

95-99% anaerobes
bacteroides, clostridium, bifidobacteria
aerobic bacteria
gram -ve bacilli
E. coli, Klebsiella, enterobacter, proteus, citrobacter

28
Q

what are the benefits of normal flora?

A
  1. synthesis and excretion of vitamins, eg. via K and B12 secreted by enteric bacteria
  2. colonisation resistance by environmental manipulation and production of antibacterial agents
  3. induction of cross-reactive antibodies may have a protective effect
29
Q

how can normal flora become pathogenic?

A
  1. overgrowth, e.g vaginal thrush
  2. translocation - presence on the wrong site - eg. through spread or inoculation
  3. cross-infection eg. MRSA