Flashcards in Microflora Deck (63)
how many microbial cells are there in our body?
10^14 - this is 10x the amount of human cells
what is meant by organisms density varies at different sites of our body?
dry, exposed areas of skin harbour far fewer organisms that protected, moist areas of the skin such as groin, armpits or toes. The highest density is in the oral cavities and colon.
what is meant by normal flora/microbiota?
organisms found in a given location in a state of health
what is meant by colonisation?
establishment in a site of the body
what is meant by microbiota?
all the organisms in a given community
what is meant by microbiome?
all the genes present within the microbiota
what is meant by symbiosis?
two or more organisms that co-exist in close physical association - human host and normal flora have a symbiotic relationship
what is an example of mutualism?
nitrogen fixing bacteria and legumes
what is commensal flora?
why is it difficult to define the extent to which human microbe relationships are commensalistic or mutualistic?
it is unclear what the role of flora is currently
what is commensalism?
when one organisms benefits but the other derives no benefit or harm
what is mutualism?
when both organisms benefit
what is parasitism?
when one organisms benefits at the expense of the other
what is neutralism?
when neither organism derives any benefit or harm
what is a non sterile site?
it is a site that has normal flora that is exposed to the environment either directly or indirectly.
why do non sterile sites exist?
until birth sterility is maintained but the baby is born and acquisition of normal flora begins. There is no mechanism to maintain sterility.
where are there differences in the acquisition of non sterility?
through C section compared to birth canal and through breast feeding (lactobacillus and bidiobacteria) and bottle feeding (enterobacteriacae)
what are sterile sites?
they have no normal flora - sterility is maintained through cleaning surfaces, physical separation from non sterile sites and barriers
what is special about barriers for sterility maintenance?
they have uni-directional flow - adjacent to non sterile sites e.g. upper genital tract separated by cervix
what influences locations of growth?
microenvironments and tissue tropisms
where are the microenvironments?
within a tissue or at different sites
what is tissue tropism?
propensity for a particular organism to grow in a particular habitat
what physical variables influence what organisms grow where?
nature of surface
what are the characteristics of skin?
subject to abrasion
2m^2 in adults
what is the gingival crevice?
it is in the mouth and is moist, constant temperature and has few physical challenges. It is an anaerobic environment with a mucosal surface component that is bathed in nutrients
why is there such a diversity of microbes in the mouth?
there are different ecological systems - soft tissue, non-epithelial, anaerobic
where are you most likely to find Actinomyces in mouth?
on the teeth - non-epithelial surface
how do humans adapt to the environment?
mouth, skin and nasopharyngeal flora, vagina and GIT
what is found in skin flora?
propionibacterium species (acne), coagulase-negative-staphylococci and staphylococcus aureus