Normal microbiota Flashcards
define normal flora
Organisms found in a given location in a state of health.
define colonisation
Establishment at a site in the body
define symbiosis
Two or more organisms co-exist in close physical association
There are 4 types of symbiosis
Mutalism
Neutralism
Commensalism
Parasitism.
define mutalism
both organisms benefit from symbiosis.
define neutralism
neither organism derives benefit or harm
define commenalism
one organism benefits and the other derives neither benefit or harm.
define parasitism
One organism (parasite) benefits at the expense of the other (host)
define non sterile
have normal flora
define sterile
no normal flora
where are non sterile sites found
where the body is exposed to the environment either directly or indirectly.
examples of non sterile sites
skin, conjunctiva, vagina, GI tract, Nasopharynx.
name 3 mechanisms which help to maintain sterile sites
surface cleaning
barriers that allow unidirectional flow- when adjacent to a non sterile site.
physical separation from non-sterile sites (closed sites)
example of a sterile site which is maintained by cleaning
lower respiratory tract.
example of a sterile site maintained by a barrier
upper genitals-cervix
Urinary tract- urethra
Middle ear- eustachian tube
example of a sterile site maintained by physical separation
pleural cavity
peritoneal cavity
spinal cord and meninges.
what are the physical variable which determine where an organism grows
moisture, temperature, pH, O2 availability and nature of surface.
what are the factors in skin which are relevant to which organism grow here.
variable temperature dry subject to abrasion aerobic environment nutrient-poor skin surface components.
what are the factors in Gingival crevice (gum) which are relevant to which organism grow here.
constant temperature moist few physical challenges anaerobic environment bathed in nutrients muocosal surface components.
what are the main organisms which affect the skin (skin flora)
coagulase negative staphylococci (staphylococcus epidermis)
staphylococcus aureus
Propionbacterium species
what are the main organisms which are found in the mouth
Viridans/oral streptococci
Anaerobes
what are the main flora found in the nostrils
skin flora- S. aureus.
what is the main flora found in the pharynx
Streptococcus pyogenes (group A) Haemophilus influenzae Streptococcus pneumoniae Neisseria meningitidis S. Aureus.
what are the main flora found in the vagina prepuberty
Skin flora
Lower GI flora- mainly E.coli.
what are the main flora found in the vagina post puberty
glycogen produced due to circulating oestrogens
– Lactobacillus spp. Lactobacillus acidophilus (ferment glycogen maintain pH 3)
Skin lora
C albicans
what are the main flora found in the stomach and small intestines.
Low gastric pH inhibits bacterial growth
Predominantly aerobic bacteria
H pylori.
what 99% of the bacteria found in GI anaerobes or aerobes
anaerobes
bacteroides, clostridium, bifidobacteria.
what aerobic bacteria is found in the large intestines
Escherichia coli, Klebsiella spp., Enterobacter spp., Proteus spp., Citrobacter spp. etc.
benefits of normal flora
synthesis excretion of vitamins- K and B12.
colonisation resistance- environmental manipulation
antibacterial agents
Induce cross reactive antibodies.
what is the main cause of c difficile
antibiotic treatment.
what are the consequences and symptoms of c difficile infection
toxin is produced
diahorrhea and pseudomembranous colitis
what is the most effective treatment for C difficile
faecal transplants.
how does faceal treatment treat c difficult
increased diversity in colonic mocroflora, similar to that of healthy donor
what other conditions might faceal transplants be useful for.
MS, chronic fatigue syndrome, idiopathic thrombotic purpura, ulcerative colitis, irratible bowel syndrome, diabetes mellitus.
what problems can cause pathology at the site of normal flora
1. Overgrowth • Excessive growth at normal site 2. Translocation • Presence at the wrong site • Spread from one surface to another • Inoculation into a normally sterile site 3. Cross-infection
what is the most common cause of Inoculation into a normally sterile site (medical equipment)
catheter.
