Biology topic 6

What is in nutrient broth?

Peptone, beef extract and blood/sugars

What is in nutrient agar?

Peptone, beef extract, agar

What is selective media?

Specific balance of nutrients so only specific organisms can grow in it

Aseptic techniques

1. Hold mouth of glass in flame
2. Disinfect surface
3. Hold metal loop in flame
4. Wash hands
5. Work in convection current
6. Don’t lift agar lid at or for too long

How do you do the process of streak plating?

1. Flame inoculating loop
2. Dip in culture
3. Streak on agar plate follow lines
4. Incubate

How do you do the process of spread plating?

1. Drop sample on agar plate
2. Sterilise spreader and distribute evenly
3. Incubate
4. Pick up individual colonies to grow separately

What is the lag phase?

Bacteria adapting to environment so reproduction rate is slow

What is the log phase?

Bacteria grow at maximum rate if sufficient nutrients

What is the stationary phase?

Death rate=reproduction rate as lack of nutrients and build up of waste products.

What is the death phase?

Deaths exceed new ell population as conditions worsen

How do you do the process of measuring by dry mass?

1. Take regular samples
2. Filter and dry
3. Weigh

How do you do the process of dilution plating?

1. original culture serially diluted
2. Lawn plate made and colonies counted
3. Multiply count by dilution factor

How do you do the process of cell counting?

1. Dilution sample 1:1 with trypon blue
2. Count living cells and take mean

How do ou do the process of turbidimetry?

Measure absorbante of sample and use calibration graph

Good and bad of dry mass

Good: easy ad quick

Bad: only mass number not actual count

good and bad of dilution plating

Good: cheap and gives bacteria number

Bad: takes long time

Good and bad of cell count

Good: counts only living cells

Bad: kills bacteria

Good and bad of turbidimetry

Good: quick and keeps bacteria alive

Bad: no actual number and hard to differentiate between dead and alive

What are exotoxins?

Soluble proteins made and released by bacteria as they grow and reproduce. Travel in blood

What are endotoxins?

Lipopolysaccharides in outer lipid layer membrane of gram negative released when bacteria breaks down.

Gram positive

Exotoxin eg staphylococcus

Gram negative

Endotoxin eg salmonella

What happens in the 1st infection of TB?

Symptomless. Inflammatory response seals infected phagocytes in tubercles

Infection of TB

* bacteria lie dormant
* If the immune system becomes weakened, bacteria become active again
* Bacteria destroy lung tissue leading to coughing, weight loss and death

what are bactericidal antibiotics?

Kill bacteria by destroying cell wall making them burst

What are bacteriostatic antibiotics?

Stop growth and reproduction of bacteria by stopping protein synthesis and nucleic acid production. AIDS immune system.

example of bactericidal antibiotic?

Penicillin

Example of bacteriostatic antibiotic?

Tetracycline

Ways to control spread of bacteria

* screen patients on arrival and isolate if infected
* Only use antibiotics when needed and ensure entire course is completed
* Wash hands and wear suitable PPE

Transmission of ifluenza

Coughing and sneezing spread droplets

Transmission of stem rust fungus

Dormant spores carried in air

Transmission of malarial parasite

Female mosquitos saliva when feeding on blood

Ifluenza mode of infection

1. Infects ciliated epithelial cells
2. Injects viral RNA that replicates
3. Cell uses to release viruses

Stem rust fungus mode of infection

1. Produces hyphae by stomata
2. Make mycelium
3. Releases digestive enzymes that digest stem

Malarial parasite mode of infection

1. Parasite inserted by mosquito
2. Travels to liver and infects RBC
3. Lyses cells to release more parasites

Ethical difficulties with control methods?

Informed consent difficult

Insecticide affect other species

Money could be spent on education/ preventing famine

Social difficulties with control methods?

Vaccines have to be accepted

Social changes are difficult to accept

Economic difficulties to control methods?

Prevention is very expensive

Malnutrition may be bigger threat than malaria

What is used to prevent malaria spread?

* insect repellant
* Nets
* Drain large areas of standing water
* Introduce predators to kill mosquitos

3 body adaptions that help respond to infection

1. Skin consisting of keratin
2. Stomach acid that kills bacteria
3. Gut ad skin flora competes with pathogens for food and space

Non specific responses to infection

1. Inflammation
2. Fever
3. Lysozyme action
4. Phagocytosis

Inflammation

Vasodilation increases blood flow to infected area

Fever

Hypothalamus sets body temp higher o decrease pathogen reproduction rate

Lysozyme action

Enzyme that kills bacteria by damaging wall

5 steps to cell mediated response

1. Pathogen is engulfed and destroyed. It’s antigens presented on surface
2. Helped T cell attaches complementary receptors to antigens on surface
3. Activated T helper cells to mitosis into T killer cells and T killer memory cells
4. Active T killer cell bind to APC and secrete chemicals that form pores in cell membrane
5. Infected cell dies

Humoral response activation stage

1. Bacterium engulfed by macrophage
2. Macrophage acts as APC and presents antigens on MHCs
3. Binds to T helper cell
4. T helper cell activated so splits into T memory cells and active T helper cells

Humoral response effector stage

1. Antigens form APCs complementary to B cells bind and undergo endocytosis
2. B cell acts as APC and presents antigens on MHCs
3. Activated T helper cell complementary binds to APC. Produces cytokines
4. Cytokines make B cell mitosis into B memory cells and b effector cells
5. B effector cells différenciâtes into plasma cels that synthesis antibodies
6. T suppressor cells stop immune response

Active immunity

Production of antibodies by immune system

Passive immunity

Introduction of antibodies from another

Herd immunity

Enough vaccinated to make disease transmission unlikely (80-90%)

Natural active immunity

Exposed to antigen/ disease

Natural passive immunity

Crossing of mothers antibodies over placenta

Active artificial immunity

Vaccines stimulate antibody production

Passive artificial immunity

Antibodies injected into body