IMM - Microbial Flashcards
5 main infectious agents
Viruses
Bacteria
Fungi
Protozoa
Helminths
Viruses are
Obligate parasites
Obligate parasites
Need a host to replicate
How do viruses divide
Budding or cytolysis (transmitted out of cell) - they also show host specificity and replicate using host cell nuclear synthetic machinery - contain RNA or dna
Routes of infection
Faecal-oral, airborne, insect vectors, blood borne (his/hep)
Reverse transcriptase
Enzyme in retroviruses that convert the RNA genome into double stranded DNA - so that it can integrate itself with host cell machinery
Smallpox
Oblligate pathogen (human) - caused by a variola virus
Special about smallpox
Characteristic diagnostically
Polio
Virus - faecal oral route mainly
Bacteria
Prokaryotes - no membrane bound organelles
Haploid - if mutation always dominant
Dicide via binary fission
Cytoskeleton is poorly defined
Bacterial capsule
Interferes with phagocytosis
Shigella
Bacterial ; faecal-oral route ; destroys epithelium of GI so very bloody and binds to actin in order to move from cell to cell
Neisseria meningitides
Gram negative - often causes meningitis or septicaemia - rapid progression - necrotic (amputation)
COLONISATION moves through human populations
nosocomial
Originating in the hospital
2 types of nosocomial infections
C.difficile ; MRSA
Mycobacterium TB
Better vaccines needed + tools for early diagnosis (using fluorescent 18F in thoracic cavity) - greater metabolic activity
Helicobacter pylori
Leads to peptic ulcer and gastric cancer ; multiple flagella so very motile
Mutation rates?
Point mutation rates are very very low 10^-8 for humans and bacteria BUT generation time for bacteria is a lot lower hence greater chances of mutations being prevalent (also HAPLOID)
Fungi
Eukaryotic - systemic/mucosal/cutaneous mycoses
What does fungi occur as?
Yeasts or filaments or both
Cutaneous meaning
Relating to the skin
Filaments
Hyphae
Protozoa
Unicellular eukaryotic (intestinal/blood.tissue parasites)
How do protozoa divide?
binary fission (double the size) or by formation of trophozoites inside a cell
trophozoites?
Active/feeding stage - begin to encyst
Infected cells ready to release into the bloodstream
Malaria
Entirely dependent on vector - latitude and altitude
Leishmania
Sandfly vector ; blood and tissue parasite and formation of trophzoites inside the cell
Visceral
Internal organs of the body
Helminths
Metazoa - eukaryotic - life cycles outside human host - main is faecal-oral transmission (hatch in gut and larvae travel different organs)
Worms
Roundworms
Flatworms
Tapeworms
Schistosomiasis
Very inflammatory ; bury into exposed skin - snail is the intermediate host
