Microbial Infection Flashcards
What is a capsid and what is its function?
Protective protein coat
Provides protection for the viral genome against environment; receptor recognition
What is a spike projection (protein)?
Glycoprotein (found within phospholipid envelope) involved in receptor recognition and viral tropism (helping virus to productively infect a cell), e.g neuraminidase and haemagglutinin expressed on Influenza A
Outline the steps of Mycobacterium tuberculosis infection.
- Bacteria first encounters alveolar macrophages. Other macrophages and APCs recognise and phagocytose the bacteria (form a phagosome).
- Phagosome matures and fuses with endosomes and lysosomes. Activation of macrophage by IFN-gamma promotes bacterial killing by ROI and RNI formation.
- APCs and activated macrophages present antigen on MHC II molecules.
- Specific CD4+ cells are activated, proliferate and differentiate into Th1 cells.
- Th1 effector cells migrate to lungs through chemotaxis - release cytokines -increased macrophage activation and triggering of potent anti microbial activities.
- Granuloma forms with centrally located macrophages (plus lymphocytes, NK cells, DCs, neutrophils)
What happens in the pre-erythrocytic stage of the malaria cell cycle?
During mosquito bite, sporozoites are released from mosquito salivary glands:
- enter bloodstream
- circulate to the liver
- invade hepatocytes
- differentiate
After one week, infected hepatocytes rupture, releasing merozoites into the bloodstream that invade red blood cells.
What happens in the erythrocytic/ blood-stage of the malaria cell cycle?
Parasite development: mature from rings to trophozoites to fully mature schizonts (contain 16-20 merozoites) over a 44-72 hr period. Schizonts eventually rupture (along with RBC) releasing more merozoites into the bloodstream (new cycle begins). This stage is where acute clinical symptoms appear.
What fungal species most commonly causes human disease and what kind of infections does it cause (with examples)?
Candida albicans
Mucosal, e.g vulvovaginal candidiasis (thrush)
Systemic, e.g disseminated candidiasis
What molecule do HIV viruses target and on which cells?
CD4 molecule on CD4 + T cells (interacts with CXCR4 co-receptor) and monocytes (CCR5 co-receptor).
Interaction between CD4 molecule and viral envelope glycoprotein gp120.
What are viruses and how do they replicate?
Intracellular obligate parasites
Replicate using host-cell nuclear synthetic machinery
Divide by budding out of host cell or cytolysis
Do viruses show host specificity?
Yes - but infect most other life forms, inc. bacteria
List viral routes of infection
Faecal-oral, airborne, insect vectors, blood borne
What makes HIV a retrovirus?
RNA used to make DNA via Reverse Transcriptase
Whereas normally in viruses DNA makes RNA which makes the protein
Give an example of a virus
Smallpox (variola virus)
What makes Prokaryotes more susceptible to the effects of a mutation?
They are haploid so if one gene is mutated, the effect will occur.
However in diploid cells, the mutation must be seen on both copies of DNA to occur.
What is the main component of Prokaryotic cell walls?
Peptidoglycan
How do Prokaryotes divide?
Binary fission
What are the purpose of the pili (several pilus) on Prokaryotes?
They can have a role in movement, but are more often involved in adherence to surfaces, which facilitates infection, and is a key virulence characteristic.
Give an example of a bacterial pathogen and it’s mode of transmission.
Shigella species
Faecal-oral route
Invades and destroys guts cells
Cell-to-cell spread using host actin
What must be taken into consideration when making vaccines for Neisseria meningitidis?
Multiple serogroups - different sugar capsules
Vaccines must target the different serogroups
Why are the mutation rates of viruses higher than humans?
They have half the point mutation rate as they have error prone replication and cannot deal with errors in genetic code efficiently.
Much shorter replication times
What types of infection do fungi cause?
Cutaneous, mucosal and systemic
What forms do yeast exist in?
Yeasts and filaments
What are Protozoa and how do they replicate?
Unicellular eukaryotic organisms including blood, intestinal and tissue parasites
Replicate in the host by binary fission or trophozoite formation in cells
How is a Protozoa infection acquired?
Ingestion
Vector transmission
Compare malaria and leishmaniasis
Both caused by blood and tissue parasites -Plasmodium (malaria) and Leishmania species (Leishmaniasis)
Both replicate by trophozoite formation inside cells
Malaria transmitted via mosquito vector whereas leishmaniasis transmitted via sandfly vector
