Lecture 35 Flashcards
What are the possible symbiotic relationships?
Mutualism: beneficial to both
Commensalism: essentially neutral to one, helpful to the other
Parasitism: harmful to one.
Where are most normal intestinal microflora found? roughly how many?
In the colon with the appendix roughly 10^9 to 10^12.
What difference occurs to microflora based on birth?
Those born by c-section will have different microflora to vaginal delivery.
What are opportunistic pathogens? Why might this occur?
Commensal bacteria which are part of the normal microflora that can become harmful. This may occur due to immune suppression (e.g HIV, cancer or transplant therapy). Depletion of the normal microbiota or displacement of the normal microbiota to a new location.
What are Koch’s postulates? What is it for? What study is this known as?
These are used to determine the causative agent of a disease, there a four:
- the suspected germ must be present in every case of the disease.
- The germ must be isolated and grown in pure culture.
- The cultured germ must cause the disease when it is injected into a healthy, susceptible experimental host.
- The same germ bust then be reisolated from the diseased experimental host.
What are some exceptions to Koch’s postulates?
Leprosy: we can’t grow this in the lab.
Syphilis: can’t grow this in the lab either.
Other exceptions are those caused by combinations of pathogens e.g liver cancer (hepatitis B and D), periodontal disease (variety) or those caused by apparently normal bacteria becoming pathogens.
What do disease causing bacteria typically get measured by? What is not typically measured?
Pathogenicity: the ability to cause disease, virulence: ability to infect and cause disease. Neither of these relate to the severity of the disease.
What are some microbial virulence factors and functions?
Adhesions: bind to host cells, siderophores: bind iron, capsules: resist phagocytosis, endotoxins: cause inflammation, exotoxins:makes the microbe cytotoxic.
What are some adhesin examples?
Physical adhesions like fimbriae: a filamentous protein projection on the surface of cells, these aid adhesion to solid surfaces like the mucosal epithelium. Could also be sex pili (these are fewer and longer) which allow conjugation between bacteria.
Chemical adhesins allow binding to tissue receptors.
What is incomplete phagocytosis? What else can a capsule do?
Incomplete phagocytosis is when the bacteria gets engulfed but the capsule prevents fusing of the phagosome and lysosome, the bacteria can then reproduce in the cell. Another possibility for the capsule is to prevent engulfing.
What are the main differences between the two toxin types?
Endotoxins: found in gram negative cell walls as lipopolysaccharides, they make poor antigens but are heat stable and cause fever, they are endogenous weak toxins with similar structures.
Exotoxins: A protein secreted by gram positive cells. An immunogenic an easily heat altered cytotoxic/neurotoxic exogenous substance which could be potent (fatal) and have variable structures.
What effects can the release of endotoxin have? Why does it get released?
induces effects such as fever, inflammation, diarrhea, shock and blood coagulation. Released as the cell wall breaks down(bacteria dies).
What effects can exotoxins have?
Many e.g release of cytotoxin kills host cells or release of coagulase forms a clot around the bacteria to protect it or can allow bacteria through cells, to name a few.
