2. Microorganism attack and body defences

Question 1

What are the 4 physical requirements for pathogen survival?

Answer 1

1. Moisture levels = most require moisture. The exception is Clostridia which is bacteria which form endospores.
2. pH - most prefer neutral 6.5 - 8.5. The exception is Helicobacter pylori which is adapted to grow in acid by producing ammonia to neutralise stomach acid
3. Temperature - most prefer body temp 37 deg. Some exceptions are Rhinovirus, Coronavirus 33 deg. And Mycobacterium leprae bacillus (Leprosy) 30 deg.
4. Oxygen for aerobic microorganisms

Question 2

Before antibiotics, what was malaria fever used as a treatment for?

Answer 2

Syphilis and Gonorrhea.
This is because malaria could easily be treated with quinine and it was less serious than syphilis.
This worked because malaria would cause the body to increase in temperature, and the high temperature would result in syphilis and Gonorrhea microorganisms dying.

Question 3

How do anaerobic bacteria multiply?

Answer 3

They multiply in anoxic tissues, where blood supply is interrupted.
E.g. Clostridia bacteria is anaerobic bacteria causing gangrene (death of soft tissue). Blood supply could be interrupted by diabetes or HBP resulting in gangrene.

Question 4

What is a treatment for gangrene?

Answer 4

Gas gangrene treatment. Hyperbaric (oxygen rich) chamber. Lots of O2 so anaerobic bacteria like Clostridia won’t be able to multiply and survive.

Question 5

Describe how someone may end up with diabetic foot disease

Answer 5

High blood sugar damages the nerves. Results in peripheral neuropathy (nerve damage). This lead to a loss of sensation so may not feel pain, pressure or injuries to the foot. These ulcers are prone to infection by anaerobic bacteria = Gangrene (tissue death)

Question 6

Give some examples of how the body protects itself by producing a range of toxic chemicals

Answer 6

1. Bile salts from intestines
2. Skin fatty acids from sweat and subaceous glands
3. Lysozyme in tears, mucus and saliva

Question 7

How does the body withhold the Iron that bacteria need?

Answer 7

Nutritional immunity:
Iron binding proteins like transferrin stay binded to iron and only removes when needed. e.g. tears have lactoferrin.

Question 8

How does bacteria overcome the iron restriction?

Answer 8

Have siderophores which have high affinity to iron. The receptors attach to our body’s iron binding proteins to try to steal the iron.

Question 9

What do the pathogenic bacteria need to compete against?

Answer 9

Friendly bacteria compete with pathogenic bacteria.
1. Friendly bacteria produce bacteriocin proteins to inhibit pathogenic bacteria growth
2. Compete for receptor sites on epithelial cells
3. Alter the pH of environment to kill pathogens
(This is another reason why we need to be careful about antibiotic intake as the friendly bacteria can also die)

Question 10

Name a microbe which can overcome our mechanical defences and explain how it does it

Answer 10

Microbial flora are adapted. Some have flagella to propel them through mucus and some bacteria produce mucinase.

Question 11

Which syndrome results in no tears or saliva?

Answer 11

Sjogrens syndrome, so can get corneal and oral infections.

Question 12

What is Ophthalmia neonatorum?

Answer 12

The baby’s eyes are contaminated during passage through the birth canal from a mother infected with either:
Neisseria Gonorrhoeae (onset 1 week after birth)
Or
Chlamydia trachomatis
(onset 2-4 weeks after birth)