B5 - Communicable Diseases

What are communicable diseases?

Diseases caused by pathogens.

What are non-communicable diseases?

Diseases that can’t be transmitted from one person to another.

What are the main factors affecting health?

• Diet

• Stress

• Life Situations

What can immune reactions initially caused by a pathogen lead to?

Allergies

Which are bigger, viruses or bacteria?

Bacteria are bigger than viruses.

What are bacteria?

Single-celled living organisms.

What are the uses of bacteria?

• Food

• Sewage treatment

• Medicine

How do bacteria cause disease?

• Divide rapidly through binary fission.

• May produce toxins.

• Sometimes directly damage your cells.

How do viruses cause disease?

• Take over the cells of your body.

• Live and reproduce inside the cells, damaging and destroying them.

What are common disease symptoms?

• High temperature.

• Headaches

• Rashes

How can pathogens spread?

• By air

• Direct contact

• By water - through digestive system.

Why do scientists culture microorganisms?

To find out more about them.

What is needed to grow microorganisms?

• A culture medium containing nutrients.

• Cooled agar gel in a petri dish.

What is a mutation?

A change in the DNA.

Why’s the maximum temperature at which cultures are incubated in schools 25°C?

Because if you cultured at 37°C there would be a high risk of growing dangerous pathogens.

Why are some bacterial cultures often grown at higher temperatures?

To enable microorganisms to grow more rapidly.

List ways to prevent the growth of bacteria.

• Raise or lower the temperature.

• Use chemicals (disinfectants, antiseptics, antibiotics, etc.).

What’s a disinfectant?

A chemical used to kill bacteria.

What is an antiseptic?

A disinfectant that is safe to use on human skin.

What is an antibiotic?

A chemical used inside our bodies, killing bacteria or preventing them from growing.

Describe the required practical investigating the effect of antibiotics/antiseptics on bacterial growth.

Equipment:

• Agar plate

• Heatproof Mat

• Filter Paper Discs

• Three antiseptics

• Disinfectant bench spray

• 1% Virkon disinfectant

• Antibacterial handwash

• Foreceps

• Clear tape

• Hand wash

• Permanent marker

• Incubator set to 25°C

Method:

1. Spray the working bench with disinfectant and dry with paper towels.

2. Wash hands.

3. Place the different antiseptics onto different filter paper discs.

4. Lift the lid of the agar plate at an angle and use forceps to place each filter paper disc onto the dots.

5. Tape the lid onto the agar plate securely, but losely enough that oxygen can still reach the bacteria.

6. Place the agar plate in the incubator for 48 hours.

7. Measure the diameter of the clear zones after 48 hours using a ruler. Take another at 90 degrees and calculate a mean. Do not remove the lid when taking measurements.

8. Record the results in a table, use pi x radius².

Safety:

• Wear safety goggles when handling disinfectant.

• Wash hands before and after handling bacteria.

Why did Ignaz Semmelweis insist his medical students wash their hands before delivering babies?

Because another doctor died from symptoms identical to childbed fever after cutting himself while working on a body. The women delivered by medical students and doctors who worked on bodies were also much more likely to die than the women delivered by midwives.

What did Louis Pasteur do?

He showed that microorganisms caused diseases and developed vaccines against anthrax and rabies.

What did Joseph Lister do?

Used antiseptic chemicals to destroy pathogens before they caused infection.

How would one prevent the spread of communicable diseases?

• Hand washing.

• Using disinfectants.

• Keeping raw meat away from food that is eaten uncooked.

• Coughing or sneezing into a handkerchief.

• Maintaining the hygiene of people and agricultural machinery.

• Isolating infected individuals.

What are some examples of viral diseases?

• Measles

• HIV/AIDS

• Tobacco mosaic virus

What are the symptoms of measles?

• Fever

• Red skin rash

How is measles spread?

Droplets in the air.

What can measles cause?

Blindness and brain damage, possibly fatal.

What are the symptoms of HIV?

Mild, flue like illness.

As it develops and turns to aids, it attacks the immune cells and after the initial mild illness it remains hidden in the immune system until the immune system is so badly damaged that it can no longer deal with infections.

How is HIV spread?

Sexual contact and exchange of bodily fluids.

Is there a cure or vaccine for HIV?

No.

What can prevent the development of AIDS for years?

The regular use of antiretroviral drugs.

What is a tobacco mosaic virus?

A widespread plant pathogen.

What does TMV cause?

A distinctive mosaic pattern of discoloration on the leaves as the viruses destroy the cells - affecting the growth of the plant as affected areas can’t photosynthesise.

What causes TMV?

Contact between diseased plant material and healthy plants, and insects.

What are some examples of bacterial diseases?

• Salmonella

• Gonorrhoea