9. Normal Microbiota Flashcards Preview

EMS - Mechanisms of Disease > 9. Normal Microbiota > Flashcards

Flashcards in 9. Normal Microbiota Deck (29):
1

which areas of skin harbour more organisms?

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

2

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

oral cavities and colon

3

what are normal flora?

organisms found in a given location in a state of health

4

what is colonisation?

establishment at a site in the body

5

what is symbiosis?

2 or more organisms co-exist in close physical association

6

what is mutualism?

both organisms benefit from the symbiosis

7

what is neutralism?

neither organism derives benefit or harm from the symbiosis

8

what is commensalism?

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

9

what is parasitism?

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

10

what are non sterile sites?

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

11

what are sterile sites?

those with no normal flora

12

when do humans acquire flora?

at birth

13

what are the 3 types of sterile sites?

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

14

where is sterility maintained by surface cleaning?

those places that are open to the environment
efficient cleaning by ciliated epithelium, removal of bacteria by coughing, sneezing or swallowing

15

where is sterility maintained by barriers that allow unidirectional flow?

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

16

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

close cavities eg. plural and peritoneal cavities, meninges

17

what factors influence what organisms colonise in which areas?

moisture
temperature
pH
oxygen availability
nature of surface

18

skin flora

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

mouth flora

viridian's/oral streptococci
anaerobes

20

what is the benefit of colonising in the mouth?

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

21

nasopharyngeal flora - nostrils

skin flora
Staph aureus

22

nasopharyngeal flora - pharynx

step. pyogenes
haemophilus influenzae
step. pneumoniae
Neisseria meningitidis
S. aureus

23

vaginal flora - pre-puberty

skin flora
lowe GI flora, mainly E. coli

24

vaginal flora, prost puberty

lactobacillus acidophilus
skin flora
C. albicans

25

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

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

GI tract - stomach and small intestine flora

acid tolerant lactobacilli, H. pylori
due to inhibition of bacterial growth by low pH. predominantly aerobic becteria

27

Gi tract flora - large intestine

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

28

what are the benefits of normal flora?

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

how can normal flora become pathogenic?

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