Topic 6: Immunity, Infection and Forensics Flashcards
1
Q
How it time of deaths determined?
A
- extent of decomposition
- stage of succession
- forensic entomology
- body temperature
- degree of muscle contraction
2
Q
How can the extent of decomposition help determine the time of death?
A
Time of deaths can be determined as decomposers such as bacteria and fungi in a specific sequence. It can also be be established by visual appearance (skin will become a greenish colour).
1. Green discolouration
2. Gases released from decomposition causing bloating and blistering
3. Tissues liquify, causing gas to be released
4. After a few month only skeleton remains
3
Q
Why can stage of decomposition not give an accurate representation of time of death?
A
As it is influenced by wounds to the body and environmental conditions (temperature, humidity and oxygen concentrations).
4
Q
How does stage of succession indicate time of death?
A
Time of death can be colonised by different species at different times after death.
1. Colonised by bacteria which decomposes tissue
2. Decomposition by bacteria provided favourable conditions for flies and their larvae
3. Decomposition by flies and larvae produce favourable conditions for beetles.
5
Q
Why does stage of succession may not give an accurate representation of time of death?
A
The stages will differ depending on the
- location of the body (soil, coffin, under water)
- environmental conditions (temperature, humidity and oxygen concentration)
6
Q
How does forensic entomology indicate time of death?
A
Time of death can be determined because the body is colonised by different species at different times after death, such as flies and beetles which have life cycles that follow a specific sequence.
7
Q
Why may forensic entomology not give an accurate time of death?
A
Influenced by
- location of body
- environmental conditions (temperature, humidity, oxygen concentration and drugs)
8
Q
How can body temperature indicate time of death?
A
Time of deaths can be determined because body temperature decreases with time after death due to a lack of exothermic chemical reaction. The process of ‘cooling down’ is known as algor mortis
9
Q
Why may body temperature don’t give an accurate time of death?
A
Influenced by
- ambient temperature
- position of body
- clothing
- humidity and air movement
Additionally this is useless after 24 hours because the body temperature will equal ambient temperature.
10
Q
How can degree of muscle contraction indicate time of death?
A
Time of death can be determined because muscles stiffen between 3-36 hours after death. This is because of the lack of oxygen, causing anaerobic respiration to take place producing lactic acid, and pH to decrease. The decrease in pH denatures respiratory enzymes inhibiting respiration and the production of ATP, causing muscles to contract. This process is called Rigor mortis.
11
Q
Why may degree of muscle contraction not indicate an accurate time of death?
A
Influence by
- environmental conditions (temperature, humidity and oxygen concentration)
- size of the Jody
- degree of muscle development
- fitness/active before deaths
- degree of ATP storage
Additionally, useless after 36 hours, ask muscles break down and relax.
12
Q
What factors should be considered when determining time of death?
A
Ambient temperature > influences rate of decomposition and forensic entomology. This is because greater temperature will increase the rate of enzyme controlled reactions. Also size of temperature gradient (heat loss).
Location > inside, underground, under water ect influence stage of succession and forensic entomology
Body position > affects the surface areas available for heat exchange, influence the rate of heat loss
Body size > surface area available for Heath exchange, heat loss
Clothing > amount of insulation, influencing heat loss
Humidity > affects amount of evaporation, influences heat loss
Air movement > influences heat loss
13
Q
What are decomposers?
A
Decomposers are microorganisms such as bacteria and fungi which are responsible for the decomposition of organic matter and the recycling of carbon.
14
Q
How do microorganisms decompose organic matter?
A
Decomposers excrete digestive enzymes which break down organic compounds into smaller ones.
15
Q
What is the role of microorganisms in the carbon and nutrient cycle?
A
As microorganisms actively take part in decomposition they are respiring, releasing carbon into the atmosphere. Additionally, the break down of plant matter and animals releases CO2 and methane from its biomass which are released into the atmosphere. The carbon in the atmosphere can then be absorbed by green plants through photosynthesis creating them back into organic substances.
16
Q
What affects the rate of decomposition?
A
The rate of decomposition is influenced by
- temperature
- oxygen concentration
A higher temperature up to optimum will increase the kinetic energy of the digestive enzymes causing more enzyme substrate complex’s to form. Beyond optimum the enzymes will become denatured.
17
Q
What is DNA profiling?
A
A process that is used to identify and determine genetic relationships between different organisms. (Except identical twins)
18
Q
How DNA profiling work?
A
It is possible as every organism profile is unique. It works by analysing the introns in an organism DNA. These introns are sections of DNA that are non coding, numerous and very variable meaning each organisms DNA profile is unique as it will contain a random combination of introns.
19
Q
What is the polymerase chain reaction?
A
A process that is used to replicate DNA in order to increase the size of a sample of DNA.
20
Q
What are the steps in the polymerase chain reaction?
A
- Denaturing, the reaction mixture is heated to 95oC which breaks the hydrogen bonds that hold the two DNA strands together.
- Annealing, the temperature is decreased to 50-60oc so that the primers can anneal to the ends of the single strands of DNA
- Elongation, the temperature in increased to 72oc as this is the optimum temperature for Taq polymerase to build,d the complementary strands of DNA to produce the new identical double stranded DNA molecules.
Each of these cycles doubles the amount of DNA.
21
Q
What is required for a PCR reaction?
A
- DNA or RNA
- primers (shirt sequences of single stranded DNA, identify where DNA polymerase enzymes needs to bind)
- DNA polymerase ( Taq polymerase)
- free nucleotides
- buffer solutions (optimum pH)
22
Q
What is the process of DNA profiling?
A
- Source of DNA is obtained (hair, salvia)
- DNA amplified using PCR
- DNA separated into fragments using restriction enzymes
- DNA separated by size/length using gel electrophoresis
- Southern blotting is used
- DNA profiles are analysed and the total number of bands, position of bands and size width of bands.
23
Q
What is the process of gel electrophoresis?
A
- DNA is added to wells in a slap or agarose gel using a micropipette
- Agarose gel covered in buffer solution (that can conduct electricity)
- Electrical currents psi lasses through the gel for 20 minutes.
- The electrical current causes the negatively charged DNA to move through the gel towards the anode
- The shorter DNA moves faster and further spreading the DNA into bands
24
Q
How do restriction enzymes work in gel electrophoresis?
A
Before gel electrophoresis restriction enzymes cut the DNA into pieces at specific locations (will always cut between sections
of repeats bases)
25
What is southern blotting?
When an alkaline buffer solution is poured over the slap after gel electrophoresis. A dry nylon filter used to absorb the fragments of stained DNA and produce visible blots.
26
What can DNA profiles be used for?
- genetic relationship ps between peoples (Paternity test)
- selective or captive breeding programmes
- identify criminals
If two DNA profiles are identical the samples will either be from the same person or identical twins, if they are very similar the samples would be from a closely related organisms that have a common ancestor.
27
Why may a DNA profile not be accurate?
- can be contaminated /at any stage of the process)
- only a small proportion of DNA is analysed
28
How does a bacteria cell differ from a eukaryotic cell?
Bacteria are small singled cells prokaryotes they differ from eukaryotic cells as
- prokaryotic cells are slot smaller
- no membrane bound organelle
- smaller ribosomes 70S compared to 80S
- no nucleus instead a DNA loop and plasmids
- peptidoglycan cell wall
- folded cell wall called mesosomes
29
What is the function of plasmids in prokaryotic cells?
Plasmids are small rings of DNA that can be exchanged between cells.
30
What is the function of mesosomes in prokaryotic cells?
These are infoldings of the cell surface membrane that contain enzymes required for respiration.
31
What is the function of pili in a prokaryotic cell?
Small protein tubes that enable the bacteria to attach to other cells of surfaces.
32
What is the function of a capsule in a bacteria cell?
Sometime called the slime capsule. It helps to retain moisture to prevent the bacteria drying out and adhere to surfaces.
33
What is the structure of a virus?
Viruses are non-cellular infectious particles that are much smaller than bacteria cells. They have a
- nucleic core acid core (single or double strand of DNA or RNA)
- a protein coat called ‘capsid’
- an outer lipid layer called an envelope (contains specific glycoproteins which make up the antigen)
34
How do virus differ from a bacteria cell?
- virus’s do not possess a plasma membrane, cytoplasm or ribosomes (any internal structures)
- virus’s cannot reproduce independently whereas bacteria can
35
How do viruses reproduce?
They bind to host cells and release their nucleic acid into it. The host cells DNA replication mechanisms replicate the viral nucleic acid and replicate the virus protein coat. The new viral particles are then assembled in the host cell and the released by cell lysis (bursting)
36
How can you compare the structure of prokaryotic cells and viruses?
- bacteria are larger then viruses
- neither contain a nucleus
- bacteria contain DNA whereas viruses can have either RNA or DNA
- bacteria contain circular non linear DNA within nucleoid and plasmids whereas viruses have linear nuclei acid
- neither contains membrane bound organelles
- bacteria has internal structure (ribosomes plasmids p) whereas viruses don’t
- bacteria reproduce independently (binary fission) and viruses can’t
37
What is Tuberculosis?
TB is an infectious disease caused by the bacteria ‘Mycobacterium Tuberculosis’ which affects the lungs. It suppresses the immune systems, meaning the body is less capable of fighting infections.
38
How is TB caught?
TB is communicable meaning is it spread by inhalation of infected air droplets. It can also survive in surfaces for months due to its thick waxy cell walls.
39
What is the sequence of TB infecting the body?
1. once inside the lungs TB is recognised as a non-self and is engulfed by phagocytes
2. The bacteria is sometimes able to survive and reproduce (binary fission) inside the phagocyte. It can lire dormant due to its thick waxy walls preventing lysosomes breaking it down)
3. The dormant TB can become an active infection if the number of bacteria becomes to great of immune systems in weakened by old age, malnutrition or HIV
4. This causes extensive damage to the lungs (respiratory failure p) or spread to other parts of the body
40
What are the symptoms of TB?
- fever, weakness, severe coughing caused by inflammation of the lungs
- fluid or blood in coughing caused by body cells rupturing creating cavities in the lungs
- weight loss
- organ failure (if TB spreads)
- death through organ failure or respiratory failure
41
How can TB be treated and prevented?
- treated by 3-9 moment of bactericidal antibiotics
- it can prevented by a vaccine
42
Why is the number of TB infection increasing?
- antibiotic resistance
- increased HIV infections
- increased immigration (from countries with high rates of TB and low rates of immunisation)
43
What is HIV?
HIV is an infection disease cause by a virus ‘human immunodeficiency virus’. It affects T-helper cells and phagocytic cells suppressing the immune system making he body less capable of fighting of other infections.
44
How can HIV be transmitted?
Communicable disease that be be sore as by the exchange of bodily fluids.
- sexual intercourse
- blood donation
- sharing used needles (drugs)
- from mother to child across the placenta
- from mother to child through breast milk
45
How does HIV invade the body and reproduce)
- enters T-helper cells by attaching to a receptor molecule on the cell membrane
- the HIV lipid membrane fuses to the T helper cells membrane allowing HIV to release its viral RNA into the T helper cells
- the viral RNA is used as a template by reverse transcriptase enzymes to procure a complementary strand of DNA
- the HIV then used the hosts cells enzymes to produce more viral components which are assembled to form new viruses
- the new viral HIV are released from the most cells by cell lysis (bursting) and the new HIV
Articles are then able to infect more T helper cells and phagocytic cells
46
What does the infection of HIV led to?
- the number of T helper cells and phagocytic cells decrease
- infected T helper/phagocytic cells are killed by other T helper cells reducing number further
- this reduced immunity to other diseases as T helper cells can no longer activate other type of T cells, activate B cells and stimulate phagocytic cells (no antibodies produced)
- this makes the immune system vulnerable to opportunistic infections such s TB, pneumonia and Cancer leading to death
47
What are the symptoms of HIV?
- flu-like symptoms immediately after infections
- patients may begin to suffer from opportunistic diesseases
- may progress to AID when individuals start suffering from constant infections
48
How can HIV be treated or prevented?
- there is no cure for HIV meaning death due to AID is inevitable, however the life expectancy can be extended used antiretroviral drugs (reverse transcriptase inhibitors and protease inhibitors)
- can be prevented by use of condoms, sterile needles and education
49
What are the main entry routes for pathogens?
- broken skin
- the digestive system (consuming food or drink)
- the respiratory systems (inhalation)
- mucosal system (body cavities nose, mouth)
50
What’s are the main human barriers to infection?
- skin
- gut and skin flora
- stomach acid
- lysozyme
- mucus and cilia hairs
51
How can skin provide a barrier to infection?
- provides a physical barrier against infection as it contains keratin making the skin tough and impermeable
- produce lipids which have antimicrobial properties
- if skin is damaged blood clots forms preventing infection
52
How do skin and gut flora prevent infection?
Flora are harmless microorganisms that are well adapted to their environment. This allows then to outcompete harmful pathogens for resources (space, water) limiting the number and therefor their ability to infect the body.
53
How does stomach acid prevent infection?
The stomach contains hydrochloride acid, killing any contaminated food or drink that enters the body. This is because the low pH denatures the enzymes within pathogens.
54
How does mucus help to prevent infection?
The respiratory track contain mucus, meaning when pathogens are inhaled they are trapped within the mucus and transported back out of the body by cilia hairs. Resulting in the mucus being swallowed and pathogens killed by the stomach acid.
55
How do lysozyme help to prevent infection?
- secretions of the mucosal surfaces (tears, saliva and mucus) contain the enzyme lysozyme.
- the enzyme damages bacterial cell walls causing them to burst
56
What is the definition of non-specific response?
The response will be the same regardless of the pathogen that invades the body.
57
What does the non-specific response include?
- inflammation
- interferons
- phagocytosis
58
What is the role of inflammation in the non-specific immune response?
- a pathogen is recognised as non self by immune system cells, the causes histamine to be secreted.
- histamine causes vasodilation of the arteries and capillary walls to become more permeable at the site of infection
- this allows for more blood flow, and therefore more immune system cells to reach the site of infection which attack the pathogens
- plasma proteins leave the blood causing the area to swell
59
What is the role of interferon in the non-specific immune response?
When a cell is infected by viruses the produce anti-viral proteins called interferons these
- inhibit the production of viral proteins, preventing them from replicating
- activate white blood cells involved with the specific immune response
- increase the non-specific immune repose (e.g. promote inflammation)
60
What is the role of phagocytosis in the non-specific immune response?
- during an infection phagocytes squeeze through the capillary walls in large numbers, chemical (histamine) attract phagocytes to infections site
- they reconsider the antigens on the surface of the pathogen as non-self
- the cell surface membrane of the phagocyte extends out and around the pathogen engulfing it and trapping the pathogen within a phagocytic vacuole. (Called endocytosis)
- enzymes (lysozyme) found within the phagocytic vacuole fuse with the pathogen and digesting it.
- after digestion the phagocyte will present the antigens of the pathogen of its cell surface membrane creating an antigen presenting cell initiating the specific immune response
61
What is a phagocyte?
A phagocyte is a tube of white blood cell responsible for removing dead cells and invasive microorganisms by engulfing and digesting them (phagocytosis). Examples are macrophages and neutrophils.
62
What is an antigen?
Antigens are markers on the cell surface membrane of every cell that identify it. They can be proteins of glycoproteins and can be self or non self.
63
What’s are self antigens?
Antigens produced by the organisms own body cells. They don’t stimulate an immune response.
64
What are non self antigens?
Antigens not produced by the organisms own body cells. They stimulate an immune response.
E.g. antigens on bacteria, viruses or transplanted organs
65
How does antigen initiate a specific immune response?
After phagocytosis, phagocytes (macrophages) transfer the antigens of the digested pathogen to their cell surface membrane becoming antigen presenting cells. This activates the specific immune response, with lymphocytes (white blood cells of specific immune response) are able to bind to the presenting antigens with specific receptors.
66
What is the structure of anti body’s?
Antibodies are Y-shaped molecules that consists of four polypeptide chains (2 heavy chains attached to two light chains by disulphide bonds).
- each of the polypeptide chains have a constant region (do not very within a class of antibody) and variable regions (amino acid sequence are different for each antibody). The variable region is where the antibody bonds to the antigen to form an antigen - antibody complex.
- a hinge region where the disulphide bonds give flexibility to the antibody allowing antigens binding site to be placed at different angles
67
What are membrane bound antibodies?
Membrane - bound antibodies are attached to the surface of lymphocytes. These have extra section of polypeptide chain within their heavy chains which forms the attachment to lymphocytes
68
What are non-membrane bound antibodies?
Non-membrane bound antibodies can be secreted directly into the blood. Membrane bound antibodies can become non membrane bound though splicing. This remove the extra section (introns) and exons (alternative splicing)
69
What’s are the functions of antibodies?
- bind to specific antigens triggering specific immune response
They also disable pathogens through
- pathogens emerged host cell by binding to receptors antibodies bind to the receptors preventing the pathogen to enter
- antibodies can act as anti-toxins by binding and engulfing toxins produced by pathogens
- cause pathogens to clump together (agglutination) reducing change of pathogens to spread round the body
70
What produces antibodies?
Antibodies are produced by plasma cells in in the blood stream.
71
Why does antibody activity increase with temperature?
At higher temperatures the kinetic energy of of antibodies will increase causing a greater formation of antigen-antibody complexes. Beyond optimum temperature the antibodies antigen binding sites will denature.
72
What are T-cells?
T cells are a type of white blood cell involved with the specific immune response. They have a specific cell surface receptor (T cell receptor) similar to antibodies and are specific to a particular type of antigen.
73
Where a T cells produced?
T cells are produced in the bone marrow and mature in the thymus glands. They can then differentiate into different types of T cells.
74
How are T cells activated?
They are activated when they encounter and bind to their specific antigen in the surface of an antigen presenting cell (macrophage or pathogen itself). They then divide by mitosis, and differentiate into either T helper cells, T killer cells work T memory cells.
75
What is T helper cells and there role?
T helper cell release chemical signalling molecules (cytokines p) which activate B cells and trigger the production of more T cells.
76
What is the role of T killer cells?
These bind to and destroy infected cells displaying the relevant specific antigen. They do this by breaking down the cell wall causing it to burst.
77
What is the role of T memory cells?
T memory cells remain in the blood and enable a faster specific immune repose if the same pathogen is encountered again.
78
What is a B cell?
B cells (B lymphocytes) are a type of white blood cell in the specific immune response. They have specific receptors (antibodies) on cell surface membrane allowing them to bind to antigens.
79
Where are B cells produced?
B cells are a produced and matured in the bone marrow.
80
What activates B cells?
B cells are activated when the receptor antibodies on the B cell recognises and bind to an antigen forming an antigen-antibodies complex. As well as cell signalling molecules produced by T helper cells. Once activated they divide by mitosis producing B effector and B memory cells.
81
What is the role of B effector cells?
These effector cells go on to form plasma cells. The plasma cells produce specific antibodies to combat non self antigens.
82
What is the role of B memory cells?
These are B cells that remain in the blood to allow faster immune response to the same pathogen in the future.
83
What is post transcription modification?
Post transcription modification determine whether or not the heavy chains of the antibodies contains an extra section of protein is present which allows it to attach to the antibody.
84
What are the two types of post transcription modification?
- splicing
- alternative splicing
85
What is the process of splicing?
Splicing occurs before the mRNA exists the nuclears after transcription
- the non condone introns section are removed
- the coding exons sections are joined together
Resulting in an mRNA molecule containing only the coding sequences of the genes.
86
What is an intron?
Non-coding sections of DNA.
87
What is a exon?
Codeing sections of DNA.
88
What is the process of alternative splicing?
The exons of genes can be sliced in many different ways to produce differnt mature mRNA molecules through alternative splicing. This means that a single eukaryotic gene can code for more than one polypeptide chain. Depending on the exons that are removed from the gene coding from antibody heavy chain, it can produce a membrane bounds or directly secreted antibody.
89
What is immunity?
The capacity of the immune system to recognised to recognise non-self pathogens and defend the body against them.
90
What are the differnt types of immunity?
- Active immunity
- Passive immunity
- natural immunity
- artificial immunity
91
What is the primary immune response?
The primary immune response is activated when it the first time an antigen is encounted. It consists of a non-specific immune response followed by a specific immune response.
92
Why is the primary immune response so slow?
- the number of T and B cells with the correct membrane receptors present in the blood will be low
- it will take time for the correct T and B cells to be activated and to divide and differentiate into the differnt cell types.
- it can take several days before plasma cells develop and are able to produce the correct antibodies
93
What is a secondary immune response?
When the immune system encounters the same antigens again it will launch a faster and stronger immune response.
94
What is the process of the secondary immune response?
1. The non self pathogens are recognised when their antigens bind to receptors in the cell surface membrane of phagocytic cells
2. The pathogens are then engulfed by the phagocyte through phagocytosis creating an antigen presenting cell
3. T memory cells with complementary receptors (created in a primary immune response) binds to the antigens and will differentiate rapidly to form complementary T killer cells
4. B memory cells will also bind to the complementary receptors and rapidly produce complementary B plasma cells which will rapidly produce complementary antibodies
95
Why is the secondary immune response faster and stronger?
- memory cells are present in large quantities than the mature lymphocytes at the start of the primary response. This means the correct memory cells are able to detect an antigen, activate, multiply by mitosis and differentiate much more quickly
- antibodies are produced more quickly and in larger quantities in a secondary response.
This will often elimate the pathogen before the infected person can show symptoms.
96
What is active immunity?
When immunity is gained whne an antigen enters the body triggering a specific immune repossessed. The body produces memory cells, giving the person long-term immunity
97
What is passive immunity?
Immunity that is acquired without an immune response. This means antibodies are gained from an alternative source and not by the infected person. No memory cells are produced as the persons immune system has not been activated.
98
What is active natural immunity?
Active natural immunity is immunity that is acquired through exposure to pathogens. Producing antibodies and memory cells.
99
What is active artificial immunity?
Active artificial immunity is acquired through vaccination. Producing memory cells.
100
What is passive natural immunity?
Passive natural immunity is acquired whne antibodies are indeed Jed into a baby’s immune system. This can be across the placenta or breast milk.
101
What is passive artificial immunity?
Immunity gained whne antibodies are introducted through injection or transfusion of antibodies. It’s a short term immunity and doesn’t produce memory cells.
102
What are vaccines?
A vaccine is a substance that contains dead of weakened pathogens that are injected into a patients, stimulating the primary immune response, creating memory cells and long term artificial active immunity
103
How do vaccines provide active artificial immunity?
1. Weakened or dead strains of pathogen is injected into a percent via a vaccination
2. Tiggers a primary immune response
3. As a result if the patient is infected with the pathogen a secondary immune system will take place.
104
What is the evolutionary race between pathogens and hosts?
Over time vertebrates have evolved better immune systems in order to defend themselves against non-self pathogens. At the same time pathogens have evolved better mechanisms in order to evade the immune system responses. Suggesting a race to over power each other.
E.g. HIV evasion mechanisms, TB evasion mechanism
105
What is the HIV evasion mechanism?
- kills T helper cells after in infects the. Reducing the number of cells that could detect the ore essence of the virus and activate the production of antibodies
- HIV shows antigenic variability due to high mutation rate (new strains of virus are created each requiring a new primary immune response)
- HIV prevent infected calls from presenting their antigens on the cell surface membrane making it difficult for white blood cells to recognise and destroy the infected cells
106
What is TB evasion mechanisms?
- once engulfed by phagocytes in the lungs the bacteria produce substance that will prevent a lysosome forms fusing with the phagocytic vacuole. (Preventing bacteria from being broken down)
- bacteria can disrupt the antigen presenting mechanism of phagocytes making it difficult for the immune system to recognise and destroy these cells.
107
What are antibiotics?
Chemical substances that damage bacterial cells with little or no harm to human tissue. E.g. penicillin
They can be either bactericidal or bacteriostatic.
108
What are antibiotics?
Chemical substances that damage bacterial cells with little or no harm to human tissue. E.g. penicillin
They can be either bactericidal or bacteriostatic.
109
What are bactericidal antibiotics?
Antibiotics that kill bacteria cells. This is achieved by inhibiting the enzymes involved in bacterial cells wall synthesis. As a result the bacterial cell wall is weakened meaning if cannot take the pressure generated when water moves into the cell by osmosis causing the cell to burst killing the bacteria.
110
What are bacteriostatic antibiotics?
These are she’s to inhibit the growth of bacteria. This is achived by binding to the bacterial ribosomes, inhibiting bacterial protein production. Therefor bacteria cannot produce enzymes needed for their metabolic processes reducing their development and growth.
111
Why are eukaryotic cells not damaged by antibiotics?
- they do not have cell walls
- they have different enzymes
- they have differnt ribsimes
112
Why are viruses not affected by antibiotics?
As viral particles don’t have cell walls or their own ribsomes, they instead bind to eukaryotic cells and use their protein sysnthis mechamisms.
113
What’s are hospital acquired infections?
Infection that’s a eencintrscted by a patient while in hospital. HAI are why hospital practices have been implemented in order to roevent and control the spread.
114
What is the rule in the hospital code of conduct?
In order to prevent the spread of HAI ans antibiotic resistant bacteria
- hand washing regimes for hospital staff and visitors
- fewer patients passing in and out of hospital
- hospital staff wearing suitable clothing
- sterilised equipment
- patient isolations
115
How does antibiotic resistant bacteria form in hospitals?
Antibiotics are widely used in hospitals to treat disease. This provides a selectional pressure for resistant strains of bacteria to develop.
116
What practices have been out in place to to reduce the risk of antibiotic HAIs?
- no use of antibiotics for minor infections or viral diseases
- no use of antibiotics as a preventative measure against infection
- prescriptions should only be narrow-spectrum antibiotics that only affect a narrow range of bacterial infections.
- rotate the use of different antibiotics.
117
Core practical 14: use of gel electrophoresis to separate DNA fragments or different length. Variables
Control > volume of DNA, Voltage of electrical current, time the electrical current is active
118
Core practical 14: use of gel electrophoresis to separate DNA fragments or different length. Method
1. Obtain a source of DNA from an organisms hair, skin ect
2. Amplify the DNA using PCR
3. Separate DNA into fragments using restriction enzymes
4. Add DNA into the wells in a slap or agarose gel using a micropipette
5. Cover gel with buffer solution that conducts electricity
6. Pass an electrical current through the gel for 20 minutes.
7. Use southern blotting. DNA profile is transferred onto a nylon membrane and an absorbent paper is placed on top. Increasing the longevity of the DNA profile
8. Add a fluorescent tag or a radioactive marker to make the DNA visible
9. Analyse and compare the DNA profiles in terms of the total number, location, size of bands.
119
Core practical 15: Investigate the effect of different antibitoics on bacteria. Variables
Control > type of antibiotic, species of bacteria, volume of antibitoics, concentration of bacteria, volume of nutrients, water availability, oxygen concentration
Independent > concentration of antibiotics, type of antibiotic, species of bacteria
Dependent > zone of zone of inhibitions
120
Core practical 15: Investigate the effect of different antibitoics on bacteria. Method
1. Make 5 serial dilution of antibiotic
2. Grow a culture of bacteria on an agar plate
3. Place antibitoic concentration on a paper disc
4. Place paper disc in agar plate
5. Use aseptic techniques
6. Tape lid knot Petri dish, invert and place in an incubator (20oc) for 7 degrees
7. Measure zone of inhibition
8. Repeat with other concentration of antibiotic and calculate mean, identify anomalies and increase validity.
