Normal Microbiota (10) Flashcards
Normal flora
Organisms found in a given location in a state of health
Colonisation
Establishment at a site in the body
Symbiosis
Two/more organisms co-exist in close physical association
Mutualism
Both organisms benefit from symbiosis
Neutralism
Neither organisms derives benefit or harm
Commensalism
One organism benefits, the other derives neither benefit nor harm
Parasitism
One organism/parasite benefits at the expense of the other/host
Non-sterile sites
Have normal flora (skin, vagina, conductive, nasopharynx, GI tract)
Sterile sites
No normal flora
Sterility maintained by barriers
Upper genital tract - cervix
Urinary tract - urethra
Middle ear - eustachian tube
Sterility maintained by physical separation
Pleural cavity, peritoneal cavity, spinal cord and meninges
Sterility maintained by surface cleaning
Lower respiratory tract - ciliated epithelium (cough/sneeze/swallow)
Tissue tropism
Propensity for a particular organism to grow in a particular habitat
Skin
Variable temperature, dry, subject to abrasion, aerobic environment, nutrient-poor, skin surface components
Gingival crevice
Constant temp, moist, toothbrush-physical challenge, anaerobic, bathed in nutrient, mucosal surface components
Skin flora
Coagulase-negative staphylococci (Staphylococcus epidermis)
Staph aureus/Propionibacterium acnes
Mouth flora
Viridans/oral streptococci/anaerobes
Nasopharyngeal flora
- Nostrils, 20%, S.aureus
- Pharynx
Vagina pre-puberty
Skin flora/lower GI flora (E.coli)
Vagina post-puberty
Glycogen produced due to oestrogen, lactobacillus acidophilus (ferment glycogen maintain pH 3)/skin flora/few C.albicans
GI flora
Low pH inhibits growth, aerobic - acid-tolerant Lactobacilli/H.pylori
Large intestine flora
> 400 species, 99% anaerobic (bactericides, clostridium, bifidbacteria), aerobic (enteric gram negative bacilli)
Benefits of normal flora
- Synthesis and excretion of vitamins (K and B12 enteric)
- Colonisation resistance (environmental manipulation/antibacterial agents)
- Cross-reactive antibodies
What is human microbiota composition measured by?
16S RNA
Micro biome and human health
IBD, diabetes, hypertension, obesity, cancer, infection - c.diff
C.diff
Hospital acquired infection, >60 years, perturbation of normal colonic microflora allows C.difficile overgrowth > toxin production > diarrhoea (Pseudomembranous colitis)
What is main risk factor for c.diff?
antibiotic treatment
Faecal transplant used to treat?
C.diff (chronic diarrhoea and food poisoning)
Suggested faecal transplant has positive effect for
MS, CFS, idiopathic thrombotic purport, ulcerative colitis, IBS, diabetes
Pathology of normal flora
Overgrowth (thrush), Translocation (conjunctivitis/inoculation into a normally sterile site), cross-infection (MRSA)
Clinical conditions caused by normal flora
Abscesses, pneumonia, endocarditis, gastroenteritis, peritonitis, urogenital infections, dental caries, periodontal disease, pharyngitis