L15- Human -microbe interactions Flashcards
Which type of bacteria does each surface select for?
a. skin -(dry,salty,acidic)
b. lungs
c. large intestine
a. gram positive e.g. staphylococcus epidermis
b. obligate aerobe e.g. mycobacterium tuberculosis
c. obligate anaerobe e.g. clostridium spp.
(gram positive spore formers)
What’s the normal flora on:
a. skin
b. oral cavity
c. nasal cavity
a. resident- staphylococcus epidermis
transient- E. Coli
b. V. high biodiversity-
steptococcus spp.
actinomyces spp. etc.
c. Restricted biodiversity opportunistic ones.
streptococcus pneumonia
influenza etc.
How are teeth colonized?
Lots of primary colonisers attach to saliva on tooth.
e,g, streptococcus sanguis
What’s the “corn cob” formation?
In mature plaque- streptococci attached to a central bacterial rod, metabolic exchange between bacteria. Mutualistic relationship
What is the normal flora in the stomach?
( at pH 2) Only Helicobacter pylon (gram negative)
What’s the normal flora in the small intestine?
pH 4-5. low bacterial biomass. e.g. enterococci and lactobacilli
What’s the normal flora in the colon? pH7
Huge bacterial biomass
Facultative aerobes e.g. E coli and Enterococcus faecalis.
-> Grow use all O2 and produce anaerobi conditions
What’s the influence of antibiotics on normal flora?
Inhibit normal flora
If a wide spectrum antibiotic is used, “virtual” sterilisation of intestinal tract.
Opportunistic pathogens can then invade e.g. clostridium spp.
What are the benefits of normal flora?
- Make vitamins K + B12
- Prevent colonization by pathogens
- Antagonize other bactera
What are the 4 stages of microbial disease?
- Enter host
- Multiply in the host
- Interfere with host defences
- Damage host -> endotoxin or exotoxin production
What are the types of pathogenicity in bacteria?
- Commensals-> normal flora
2. Opportunistic pathogens
