Bacteria II Flashcards
define: normal flora
microorgs present on a healthy bacteria
resident vs transient flora?
always vs not always present
when are normal flora acquired?
during and shortly after pregnancy
change throughout life
where should normal flora be found?
surface tissues
uusally not in internal tissues
describe skin
resident and transient
inhospitable - low pH, high [NaCl], low moisture, antibacterial substances eg lysosyme
describe vagina
acid
lactobacilli
describe mouth
a lot: 500-600
saliva and food particles good source of nutrients, but hard for bacteria to gorw in saliva due to lysozyme
describe biofilm
found in mouth
often oxygen depleted - anaerobic bacteria flourish
describe stomach
acid resistant lactobacilli and streptococcil; some H pylori
not many at all
describe small intestine
pH, hence bacteria numbers, increase as you get furhter
duodenum –> jejunum –> ileum
describe large intestine
a lot - 400 species oxygen depleted - anaerobic thrive bacteroides :strict anaerobes e coli: facultative anaerobes others
describe respiratory tract
contains normal flora; similar to mouth
what is disease?
when body stops working
causes of disease?
infection, metabolism, genes…
what is infection
when pathogens invade tissues
what causes infection
opportunistic pathogens: WERE ONCE NORMAL FLORA
pathogens: WERE NEVER NORMAL FLORA
what are carriers?
organisms who are infected but not obviously diseased
2 types of carriers
incubatory
convalescent
why are humans great hosts?
have a lot of nutrients
stable yet variable
4 steps in infection
exposure
adherence
invasion
colony growth
2 types of exposure?
- indirect (airborne particles and contamination)
- direct (airborne, vectors, horizontal and verticle (mum -> foetus))
describe adherence
adherin and cell receptor bind
happens for pathogens and normal flora - but doesnt progress for normal flora
what happens once the bacteria colonise?
harm cells by releasing toxins and invasins
what are invasins
enzymes that harm host cell
3 types of invasins
collagenase
hyaluronase
neuraminidase
what is collagenase
clostridium
breaks down muscle collagen
what is hyaluronase
streop, staph, slostridium
breaks down connective tissue
what is neuraminidase
shigella, vibrio
degrades neuramic acid, which holds gut tissue together
2 types of toxins?
endotoxins and exotoxins
what are exotoxins
release toxins from inside
examples of exotoxins
botulimum: causes paralysys
cholera toxin: damages gut wall, causing diarrhoea
what are endotoxins
bacteria dies, LPS released
examples of endotoxins
salmonella typhis: causes typhoid
