4.3.1 Communicable Diseases Flashcards
Divine the term pathogen
A pathogen is a microorganism capable of causing disease
Four types of pathogens
Bacteria
Viruses
Fungi
Protists
2 ways pathogens can cause disease
Damaging cells - viruses ‘live’ and reproduce inside the cells, damaging and destroying them. Bacteria can also directly damage cells
Producing toxins - bacteria produce toxins (poisons) that affect your body and make you feel ill
Bacteria and viruses reproduce rapidly inside the body
How do bacteria multiply
They multiple by process of simple cell division called binary fission.
Usually divide once every 20 minutes
If a bacterial cell can divide once every 20 minutes, how many bacteria will be there after 6 hours
6 hours = 20 mins x 18
18 times
2^18 = 262144 times
Describe the growth of bacteria grown in a culture solution containing all the nutrients the bacteria need over a period of 8 hours
(Setting phase—bacteria getting used to new environment so there is no binary fission)
Bacteria divide rapidly by binary fission
Numbers increases at an increasing rate
Plenty of nutrients, not too much waste
Then the number of cells level out
Nutrients run out
Waste product builds up—CO2 and ethanol (if anaerobic)
Then bacteria will begin to die
RP2 - investigating the effect of antiseptics on the growth of bacteria
Equipment:
A nutrients agar plate
A heatproof mat
Filter paper discs
Three antiseptics—e.g. mouthwash, TCP, antiseptic cream
Disinfectant bench spray
Forceps
Clear tape
Hand wash
Chinagraph pencil
Access to an incubator (set to 25 degrees Celsius)
RP2 - investigating the effect of antiseptics on the growth of bacteria
Method:
- Spray bench with disinfectant spray. Then wipe down with paper towels
- Mark the underneath of a nutrient agar plate (NOT THE LID) with the chinagraph pencil into the 3 equal sections and label them on the edge of the plate with the 3 different antiseptics that you will use. Also mark a dot in the middle of each section. Around the edge write your initials, date and the name of the bacteria (E. coli)
- Wash your hands with the antibacterial hand wash
- Flame the neck of the bottle of antiseptic
Flame the inoculating loop/forceps
Use the forceps to pick up the filter paper discs and soak in the disinfectant - Carefully lift the lid of the agar plate at an angle DONT OPEN FULLY
- Use forceps to care fully put each disc onto one of the dots marked previously
- Secure the lid of the agar plate in place using 2 small pieces of clear tape. Do not seal lid fully because this creates anaerobic conditions, which will prevent the E. coli from growing.
- Incubate the plate at 25 Celsius for at least 48 hours
- Measure the diameter of the clear zone around each disc by place the ruler across the centre of the disc. Measure again at 90 degrees to the first measurement so that the mean diameter can be calculated
- Record results in a table
Pathogen type of measles
Virus
Pathogen type of HIV
VIRUS
Pathogen type of malaria
Protist
Pathogen type of salmonella
Bacteria
Pathogen type of gonorrhoea
Bacteria
Pathogen type of Rose Black Spot
Fungus
Pathogen type of tobacco mosaic virus (TMV)
Virus
Method of spread of Measles
Inhalation of droplets from coughs and sneezes
Method of spread of HIV
Sexual contract or exchange of body fluids, e.g. by sharing drug needles
Method of spread of malaria
Mosquito acts s a vector when feeding on blood
Method of spread of salmonella
Eating contaminated food
Method of spread of gonorrhoea
Sexual contract
Method of spread of rose black spot
Spread to plants by water and wind
Method of spread of tobacco mosaic virus
Direct contact between plants or on farmers’ hands
Symptoms of measles
Fever
Skin rash
Spots in mouths
Symptoms of HIV
Flu like symptoms initially
Immune system damaged so it cannot deal with infections/cancers
Lead to AIDS
Symptoms of malaria
Recurrent episodes of fever
Symptoms of salmonella
Stomach cramps
Diarrhoea and vomiting
Fever
Symptoms of gonorrhoea
Thick yellow/green discharge from penis/vagina
Pain on urinating
Symptoms of rose black spot
Purple or black spots on leaves
Leaves then turn yellow and drop early
Slower growth
Symptoms of TMV
Yellow ‘mosaic’ pattern on leaves due to lack of chlorophyll
Slower growth
Treatment/control for measles
Vaccination for PREVENTION
Painkillers for SYMPTOMS
Treatment/control for HIV
Antiretroviral medication to prevent AIDS development
PrEP (medicine) for prevention
Treatment/control for malaria
Prevent mosquitos breeding
Mosquito nets
Antimalarial drugs
Treatment/control for salmonella
Vaccinated poultry
Wash hands with soup before preparing food and after using the toilet
Cook food thoroughly
Treatment/control for gonorrhoea
Barrier contraception (condoms)
Antibiotics, but many species are resistant to penicillin
Treatment/control for rose black spot
Remove and burn infected leaves
Use fungicide sprays
Treatment/control for TMV
Disinfect tools and hands when handling plants
Burn infected leaves
What causes the symptoms of salmonella—vomiting and diarrhoea?
Toxins
Body defences where??
Lining of nose and trachea
Eyes
Stomach
Skin
Scabs
WBCs
Body’s defences: lining of nose and trachea
Secrete mucus to trap bacteria
Cilia waft the mucus up and OUT of the lungs
Body’s defences: eyes
Tears contain enzymes which kill pathogens
Body’s defences: stomach
Contains HCl (pH 1-2)
Kills pathogens
Body’s defences: skin
Dead layer of cells which forms a protective barrier to stop pathogens entering
Produces sebum which is antiseptic so kills pathogens
Body’s defences: white blood cells
Make antibodies
Engulf pathogens
Make antitoxins
How do general WBCs kill pathogens
WBCs release antitoxins which bind to the toxins released by the pathogens. This neutralises them
How do phagocytes kill pathogens
Phagocytes engulf and ingest pathogens by using their digestive enzymes
How do lymphocytes kill pathogens
Lymphocyte makes and releases specific antibodies (?)
They are complementary to the antigens on the pathogen
They bind to the antigens and kill the pathogen
What is the primary response
When you have been exposed to a particular pathogen you will have produced antibodies specific to that pathogen. Some of the lymphocytes that produced these antibodies stay in the circulatory system—memory cells
Secondary response
If you are exposed to the same pathogen again, the lymphocytes can quickly produce the specific antibodies again in very large numbers so that the pathogen is destroyed.
Happens so quickly that the pathogen does not have the chance to reproduce and start to release toxins
The infected individual does not suffer from any symptoms—they are immune to the pathogen/disease
Secondary response
___. Slower to decrease
/. _
/. \
/
1 response /
. /
/ \ /
_____/. \_________/
Types of immunity
Active immunity—primary+secondary responses
Passive immunity—receive antibodies from someone else who has already had the infection:
Breast feeding—baby has short term protection from some infections
Via the placenta during pregnancy, e.g. whooping cough
Injection of another person’s antibodies, e.g. COVID, anti-venom
Which diseases do we currently have successful vaccination programs for
Malaria
Yellow fever
Meningitis
Hepatitis
Tetanus
Polio
Rubella
Measles
Mumps
HPV
Which part of the pathogen must be included in the vaccination if it is going to stimulate an immune response response
The antigen
How does vaccination provides immunity against disease
- Vaccination—Dead/weakened pathogen is injected into the body
- Primary response—WBCs produce specific antibodies against the antigen delay (slowly)
- Secondary response—‘real’ pathogen enters, WBCs produce MORE antibodies MORE rapidly, kill pathogen
- Immunity—pathogen doesn’t reproduce, no symptoms of the disease! :)
Groups of people who are not ale to be vaccinated
People on immuno-suppressants
Newborn babies
Elderly
People with HIV
Cancer patients
Vaccines don’t work on some people (rare)
Why might some people choose not to be vaccinated
They think they’re protected by herd immunity
Close
Adverse effects
Propaganda
Religious reasons
Herd immunity
By vaccinating a large proportion of the population, the spread of disease is also reduced this is because there are fewer individuals within the population who can become infected and spread the disease
No one is vaccinated—pathogen spreads through the population
Some of the population is vaccinated—pathogen spreads through some of the population
Most of the population is vaccinated—spread of the pathogen is contained
Painkillers vs antibiotics
Painkillers help relieve the symptoms of an infection but don’t kill the pathogen that is causing it
Antibiotics kill the pathogen that is causing the disease
How do antibiotics work
Penicillin works by killing bacteria inside the body
Not all antibiotics wok on all bacteria, therefore it is important that the correct antibiotic is used to treat a specific infection
The use of antibiotics has greatly reduced deaths from infectious bacterial dieseases
Bactericidal antibiotics vs bacteriostatic antibiotics
Bactericidal antibiotics kill bacteria
Bacteriostatic antibiotics keep them from reproducing
Problems with using antibiotics
Cannot kill viruses—do not work on viral infections
Overuse means that strains of bacteria are becoming resistant to antibiotics
A good medicine must be:
Effective—must prevent/cure disease OR relieve symptoms (efficacy)
Safe—it must not be too toxic or have unbearable side effects
Stable—can be stored for some time
Dose controlled
Stages of drug development
- Drug discovery—computer simulations; identity chemicals which could potentially act as drugs
- Pre-clinical—tested on cells, tissues and organs; test for toxicity
- Preclinical—tested on animals; find out how it works in a living organism
- Clinical Phase 1— healthy volunteers; look for side effects
- Clinical Phase 2—small group of patients; test if it works (test the efficacy)
- Clinical Phase 3—large group of patients; establish the optimum dose
- Ongoing Phase 4—monitored after license granted; monitor for rare side effects or long term effects
Peer reviewed throughout
