Lect 10 - Normal Microbiota - Tue 13th Oct Flashcards
(32 cards)
what is normal flora?
Organisms found in a given location in a state of health
what is Colonisation
Establishment at a site in the body
what is Symbiosis
Two or more organisms co-exist in close physical association
what is Mutualism
Both organisms benefit from symbiosis
what is neutralism?
Neither organism derives benefit or harm
what is Commensalism?
One organism benefits, the other derives neither benefit nor harm
what is Parasitism?
One organism (parasite) benefits at the expense of the other (host)
describe the non sterile sites of the body
conjunctiva nasopharynx GI tract Vagina Skin
what maintains sterile sites?
Sterility maintained by surface cleaning
barriers that allow uni-directional flow
physical separation from non-sterile sites
what sterile site in the body is maintained by surface cleaning?
Lower respiratory tract
what sterile sites in the body are maintained by barriers?
Upper genital tract (Cervix) Urinary tract (Urethra) Middle ear (Eustachian tube)
what sterile sites in the body are maintained by physical separation
Plural cavity
Peritoneal cavity
Spinal cord and meninges
what is Tissue tropism
Propensity for a particular organism to grow in a particular habitat
what Physical variables lead to certain microbes growing
Moisture Temperature pH O2 availability Nature of surface
what is the Gingival crevice?
base of teeth near gums.
what is the normal skin flora?
Coagulase-negative staphylococci
Staphylococcus aureus
Propionibacterium species
note skin near any body orifice may be similar to those in the orifice.
what mouth flora are there?
Viridans/oral streptococci
Anaerobes
Many others
what flora in the nasopharynx are there?
Streptococcus pyogenes (group A) Haemophilus influenzae Streptococcus pneumoniae Neisseria meningitidis S. aureus
how does the vagina change in terms of micro-organisms post puberty?
glycogen produced due to circulating oestrogens.
changes from lower GI flora to Lactobacillus spp. and Lactobacillus acidophilus which Ferment glycogen.
they Maintain pH ≈3, preventing overgrowth of other species
What stomach Flora is there?
Predominantly aerobic bacteria
- acid-tolerant Lactobacilli - Helicobacter pylori
what large intestine flora is there?
95-99% Anaerobes
Bacteroides spp., Clostridium spp. Bifidobacteria spp
some Aerobic bacteria - Enteric Gram-negative bacilli
what does ssp. after a name mean?
many species of that group.
eg Clostridium spp = lots of different Clostridium bacteria.
what vitamins do you get from your flora?
vitamins K (E coli) and B12 secreted by enteric bacteria
how are you protected by normal flora?
Colonisation resistance
Induction of cross-reactive antibodies
