The Human Microbiome Flashcards
define colonisation
the establishment of microorganisms at a site in the body
define human microbiome
the microbes that live in and on the body
define resident microbiota
organisms which are found at a given location in a state of health
define symbiosis and the 3 types
when 2+ organisms co-exist in close physical association
mutualism
- reciprocal benefit
parasitism
- one side benefits - large degree of harm to the host
commensalism
- least association
- used for shelter and food
define dysbiosis
an imbalance in the resident human microbiota
define pathobiont
a member of the resident microbiota that causes disease when there is a loss of the normal balance and dysbiosis
define opportunistic infection
when an infection is caused by an organism which is a member of the normal microbiota or normally inhabits the external environment
what is a sterile site?
an area in which there are no microbes present.
what is a non-sterile site?
a site directly or indirectly exposed to the environment
which body sites are normally colonised/non-sterile?
conjunctiva
oral cavity
pharynx
vagina
skin
GI tract
how are sterile and non-sterile sites maintained?
- non-sterile - there are no mechanisms
sterile
- surface cleaning - areas open to enviornment
- barriers which allow uni-directional flow - sphincters
- physical separation - closed cavities
what body sites are normally sterile?
- surface cleaned
= lower respiratory tract - uni-directional flow
= middle ear - eustacian tube
= upper genital tract - cervix
= urinary tract - urethra
= hepatobiliary tract - sphincter of oddi - the liver, gall bladder and bile ducts - physical separation
= pleural cavity
= peritoneal cavity
= spinal cord and meninges
what can be the harmful effects caused by a distressed microbiome?
opportunistic infections may occur
what 6 factors affect the microbiome?
- moisture
- temperature
- pH
- o2 availability
- nature of the surface
- surface turnover
what is tropism
an orientation in response to a external stimulus
give 4 areas of the body which have microenvironments
skin
mouth
nasopharynx
GI tract
what are the microenvironments of the mouth?
- tooth surface
- lingual surface
- buccal surface
- gingival crevice
what is the main bacterium on our skin? where
staphylococus aureus
esp in nose
what were the 3 early colonisers in the oral microbiota?
streptococci oralis
streptococci mitis
streptococci salivaris
give 4 microbiota associated with the pharynx
streptococcus pyogenes
streptococcus pneumonia
staphylococus aureus
haemophilus influenza
describe the microbiota in GI tract.
- counts increase distally
- low gastric pH - inhibit growth
- anaerobic bacteria
- few obligate anaerobes
what are obligate anaerobes
microorganisms killed by oxygen
in the large intestines, how many organisms per gram are there?
10^9-10^10
give an example of aerobic bacteria
Enteric gram-negative bacilli
how is the microbiota in the vagina maintained?
pre-puberty
- mainly E.coli
- low microbiota
post-puberty
- glycogen produced due to circulating oestrogen
- lactobacillus streptoccoci ferment glycogen
- maintains pH 3
what are the benefits of the resident human microbiome?
- exogenous pathogens are excluded
- promotes development of immune systems
- nutrition
- enhanced cellular proliferation and wound healing
- induces antibodies
4 reasons why a opportunistic infection may occur.
- epithelium is damaged
- foreign bodies present
- immune system disturbed/suppressed
- normal microbiota disturbed
give 3 infections from which bacteria has spread from one site to another
- otitis media - ear
- conjunctivitis - eye
- UTI
