microbial disease Flashcards
(27 cards)
define pathogenicity
ability of microorganism to cause disease by damaging host tissues or producing toxins
define exotoxin
proteins secreted by a bacteria
define endotoxins
lipopolysaccharides released when bacteria die
define attachment
ligands and glycocalyx (from bacteria cell membrane) bind to specific host receptors . some enter via:
-endocytosis: where bacteria is engulfed by host cell,
-or by production of enzymes by pathogens: which damage the cell membrane of host cell)
define infectivity
-the amount of bacteria needed to cause infection.
-which varies by species
-e.g salmonella requires a large amount of bacteria whereas typhoid fever only needs a small amount.
define invasiveness
-bacterias ability to spread.
-e.g. bubonic plague and anthrax where toxins spread through the body and damage tissues far away from initial site of infection.
what are the different types of transmission of disease
-airbourne (respiratory passages)
-water-bourne
-food
-sexual intercourse (HIV, gonorrheoa)
-contact (skin/ contamination)
define viral disease
viruses are intracellur (tiny) parasites that can only reproduce inside living cells
what are the two ways viral diseases can cause disease
- by damaging the host cells when they enter and replicate
- by producing toxins during replication
structures and functions of viruses
-all viruses have: either DNA or RNA (not both); enzymes and a capsid (a protein coat)
-some also have a lipid envelope which helps them enter cells
-many have glycoproteins spikes on their surface, which acts as antigens and helps the virus attach to the host cells
whats the general way viruses replicate
1.virus enters a host cell
2.it copies the genetic material (RNA/DNA)
3.it produces new virus parts (like capsids and envelopes)
4.new viruses are formed
5.the host cell bursts open, releasing new viruses to infect other cells
describe the disease influenza
-RNA virus, only type A causes epidemics
-symptoms: fever; cough; sore throat; fatigue; headache; back pain
-transmission: droplets (cough/sneezes) by respiratory passages
-treatment: difficult to treat. body should naturally recover itself
-preventions: yearly vaccines as virus continually changes (nasal spray vaccines for children); affected people should be isolated with well ventillated rooms and sneeze/cough into tissues and dispose correctly; avoid overcrowding
describe the viral replication of influenza
1.virus enters epithelial cell in nose/throat/lungs
2.outer molecules on virus binds to receptors on cell membrane
3.once inside the virus removes its capsid (protein coat) and releases viral RNA and RNA polymerase
4.viral RNA enters host nucleus and takes over controlls protein synthesis
5.RNA polymerase synthesises viral mRNA strands and forms viral lipids and proteins
6.these are used to form new viruses
7.the cell bursts and new viruses are released, infecting other cells
describe the disease ebola
-a virus that causes lethal haemorrhagic fever syndrome
-transmission: contact with bodily fluids/bloods
-symptoms: fever, bleeding, organ failure
-treatment: no liscensed treatment ~possible treatment vaccines and experimental siRNA and ZMapp.
describe ebola replication
1.gylcoproteins on virus bind to receptors on host cell membrane
2.virus enters the cell by endocytosis
3. capsid (protein coat) is removed from virus and RNA polymerase and RNA polymerase released.
4.viral RNA is replicated, transcribed and translated to produce viral RNA and protein
5.this forms new viruses the cell burst and new viruses infect other cells
decsribe cholera
-caused by contamination of dirty (faeces) water by the pathogen vibrio cholerae
-symptoms: diarrhoea and dehydration
-treatments: ORS medicine which contain Na+ and glucose which are co-transported to epithelial cell. -where WP is now low so water moves from lumen back into epithelial cell by osmosis. –>some ORS medicine contain starch instead of glucose as glucose was seen to lower WP in lumen.
describe the mechanism of cholera
1.toxin binds to protein receptors on the epithelial cell
2.this opens Cl- channels so Cl- ions diffuse out fo cell into lumen
3.Cl- ions cause WP to be lower in lumen than blood
4.water moves into lumen by osmosis (resulting in diarrhoea)
describe tuberculosis
-an infectious disease caused by the pathogen M.tuberculosus
-transmission: droplets (sneezing/coughing/inhaling)
-develops in the lungs
symptoms: persistant cough (maybe coughing blood); breathing difficulties & chest pain; fatigue; weight loss due to loss of appetite; fever and night sweats
treatment: antibiotics but difficult to maintain as it is a 6-12 month course
prevention: BCG vaccine; improve hygiene; strengthen immune system ;isolate sufferes
decsribe how Tuberculosis infects the body
- A pathogen travels through airway into lungs.
- Phagocytic WBC engulfs the bacteria
- Bacteria form tubercles
- in healthy people the immune system prevents TB from developing further -so is inactive and doesnt replicate
5.people who suffer immunosuppression (weak immune system) bacteria is active and replicates
6.bacteria begins to damage the alveolar wall and capillaries
7.this causes fibrosis (scar tissue) and less gas exchange
8.TB then spreads and damages to the rest of the body
describe the disease AIDS
-caused by HIV which is a retrovirus so contains RNA and Reverse transcriptase (converts RNA into DNA inside host cells)
-transmission: sexual contact (semen/ vaginal fluids); blood transfusions/sharing needles ; mother to baby via pregancy/ breastfeeding.
what are the four stages of AIDs
1.early stage: flu; swollen glands; rash
2.HIV positive stage: no symptoms
3.ARC stage: minor infections; weight loss; less T-helper cells
4.Full AIDs: severe infections; death from pneumonia due to immune system failure
describe HIV replication
1.HIV binds to T-helper cells by surface glycoproteins.
2. it releases viral RNA and reverse transcriptase into the cell which makes DNA from viral RNA
3.viral DNA enters nucleus and attaches to host DNA and replicates with host DNA.
4. it could stay inactive for yeears
5.when activated, it produces new viruses and T-helper cell is destroyed as viruses are released and infects other T-helper cells
6.No. of T-helper cells in blood decreases so no stimmulation of antibodies
7.immune system weakens so person becomes prone to infections/illnesses.
how to prevent HIV
-reduce sexual transmission(use condoms)
-blood screening and organ donation
-clean needles for drug users
-mothers-to-baby risk: c-sections and bottle feeding baby
-PEP: a month long treatment taken within 72 hours of exposure to HIV -not guaranteed and has side effects
-PrEP: taken by HIV negative people before potential exposure to reduce risk.
describe malaria
-caused by tiny parasite plasmodium.
-transmission: it spreads by female anopheles mosquito
-symptoms: fever vomitting and serious cases cause severe anaemia and can cause brain damage
-prevention: nets, repellants, insecticides
