L10- Normal Microbiota Flashcards
What is Symbiosis
Two or more organisms co-exist in close physical association
Symbiosis: What is Mutualism?
Both organisms benefit from symbiosis
Symbiosis: What is Neutralism?
Neither organism derives benefit or harm
Symbiosis: What is Commensalism?
One organism benefits, the other derives neither benefit nor harm
Symbiosis: What is Parasitism?
One organism (parasite) benefits at the expense of the other (host)
Do non-sterile sites have normal flora?
Yes
Non-sterile site- Have normal flora (Exposed to the environment)
Sterile sites- No normal flora
Sterile site examples…
Lower resp tract: Sterility maintained by surface cleaning
Cervix, Urethra: Sterility maintained by barriers
Spinal cord, Pleural cavity: Sterility maintained by physical separation
Examples of Skin flora
Coagulase-negative staphylococci
Staphylococcus aureus (esp. in nasal carriers)
Vagina Microbiota Pre puberty vs Post puberty
Pre puberty: Skin flora, Lower GI flora (mainly E. coli)
Post-puberty: Lactobacillus acidophilus (ferment glycogen)
Maintain pH ≈3, preventing overgrowth of other species
Anaerobic or aerobic bacteria in stomach + small intestines?
Predominantly aerobic bacteria
Anaerobic or aerobic bacteria in large intestine ?
95-99% Anaerobes:
Clostridium
Aerobic bacteria:
Enteric Gram-negative bacilli
Benefits of normal flora
Synthesis and excretion of vitamins - e.g. vitamins K and B12 secreted by enteric bacteria
Clostridium difficile infection Major risk factor…
ANTIBIOTIC TREATMENT
—> Overgrowth of C.Diff
Leads to toxin production —> Diarrhoea, Pseudomembranous colitis
Pathology of normal flora : Example of Overgrowth
Vaginal thrush
Often treatment with broad spectrum antibiotic can lead to candida infections
Pathology of normal flora: Example of Translocation
Conjunctivitis
From one surface to another
