Need to know Flashcards
What are Kochs Postulates?
1) The micro-organism must be found in abundance is all organisms suffering from the disease but should not be found in healthy organisms.
2) The microorganism must be isolated from a diseased organism and grown in pure culture.
3) The cultured microorganism should cause disease when introduced into a healthy organism.
4) The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
-In modern times however, it has been shown that many micro-organisms that cause certain diseases do not follow some/most of these rules.
What is HIV?
- A retrovirus that causes an infectious disease, it leads onto AIDS in many cases
- It targets the bodies immune system
How is HIV spread?
- Sexual intercourse
- Needle sharing
- Breast feeding
- Exchange of bodily fluids
How does HIV cause the infection?
- Attacks wbc - CD4+
- Inserts its genes into cell’s DNA using this to manufacture more virulent particles
- CD4+ cell count decreases progressively until it reaches a threshold that means the person develops AIDS
- HIV can ‘hide’ from the body’s immune system and is only detected when virulence is too high to fight
Koch postulates and HIV cures?
- There is yet no cure for HIV/AIDS but it can be controlled with anti-retroviral drugs
- One case of ‘cure’ has been seen in a patient with leukemia who had a full bone marrow transplant, the donor had a rare genetic mutation that was resistant to the virus
- Koch’s postulates: Viruses are difficult to grow in vitro in pure cultures
What is HPV?
- A virus proven to cause cervical cancer
Does HPV fulfil Koch’s postulates?
- No as many people have one of the HPV strains without getting cervical cancer, commonly transmitted through intercourse
- Yes - known as the primary cause, experiment investigated the prevalence of HPV in cervical cancer tumours, found in 93% of them. Modern techniques found that it was prevalent in 100% of tumours
What is Vibro cholera?
- Gram -ve bacterium
- Some strains cause the disease cholera
What are the symptoms of cholera?
- Diarrhea
- Vomiting
- Severity can lead to very fast dehydration and loss of electrolytes
How does cholera cause disease?
- Usually taken into the body via infected food or water
- Enters small intestine via endocytosis
- Produces cholera toxin
- Toxin causes chloride ion protein channels in plasma membrane of small intestine epithelial cells to open up
- Chloride ions move into small intestine lumen
- Build up of ions lower water potential of lumen therefore water moves out from blood across epithelial cells into the small intestine lumen via osmosis
- Mix of water with feces to cause diarrhoea
Cholera treatment?
- Oral rehydration solution, water alone not good enough, need to replace electrolytes
- ORS is drink that contains salts like sodium and sugars like glucose
What are lactic acid bacteria?
- Gram +ve bacteria
- Low GC
- Acid tolerant
- Can be rod or cocci
- Usually found in decomposing plants and milk products
- Produce lactic acid as major metabolic product of carbohydrate fermentation
What positive effect do they have on certain foods?
- Prevent food spoilage
- Production of acid - acidification - inhibits MO growth
- Som LAB produce proteinaceous bacteriocins which also prevent MO growth
- Some studies show they produce antifungal peptides
Describe LAB metabolism
- Aerotolerant anaerobes
- Homolactic fermentors: Only produce lactic acid
- 1 molecule of glucose to 2 molecules lactic
- Unable to make and use haem & cannot make cytochromes that are key ETC components
- They produce hydrogen peroxide and need to export this into external environment therefore die in virto
What industrial uses are there for LAB?
- Food production
- Sauerkraut - Lactobacillus which produced lactic acid as well as alcohols and hydrocarbons which combine to form esters to contribute to sauerkraut’s unique taste
- Yoghurt - LAB ferment the milk to produce it. Lactobacillus bulgaricus and Streptococcus thermophilus (some laws require all yoghurts to produce these two cultures)
