Growth, Survival, and Death of Microbes

Question 1

What are the stages in the life cycle of a virus?

Answer 1

1. Attachment of the virus to the surface of a susceptible, and becomes adsorbed
2. Penetration whereby the virus enters the cell via fusion with the plasma membrane then entry via the endosome
3. Uncoating where the genome needs to made available so that it can act on the host cell DNA
4. Viral nucleic acids and proteins become synthesised in the nucleus and cytoplasm. Their assembly and maturation occurs in the nucleus, cytoplasm or the membrane
5. Lysis occurs of the cell such that the viruses can be released from the cell. Budding is another method by which viruses can be released from the cells

Question 2

What is the clinical significance of the stages in the life cycle of a virus?

Answer 2

All these stages can be targetted through vaccination or anti-viral therapy

Question 3

What is a defective virus?

Answer 3

One that requires the assistance of another virus for its propagation

Question 4

Give an example of a defective virus?

Answer 4

HDV

Question 5

What does a HDV virus require for its propagation?

Answer 5

HBV

Question 6

What is a viroid?

Answer 6

A naked ssRNA of less than 400 nucleotides

Question 7

What are prions?

Answer 7

Extremely robust ‘proteinaceous infectious particles’ lacking nucleic acid.

It seems they are normal body proteins converted to an alternative configuration by contact with other prion proteins

Question 8

Where are prions the causative agent?

Answer 8

In CJD

Question 9

How is CJD transmitted

Answer 9

Humans eating infected cow meat

Question 10

What do prions play a role in the development of?

Answer 10

Alzheimer’s disease

Question 11

Why are prions involved in the development of Alzheimer’s disease?

Answer 11

There is the formation of insoluble deposits (prions) forming in the brain, leading to neural degeneration

Question 12

How do bacteria multiply?

Answer 12

Binary fission

Question 13

In what manner to bacteria propagate?

Answer 13

Exponentially

Question 14

What are propagating bacteria known to be in?

Answer 14

The vegetative state of growth

Question 15

What is the problem with bacteria in the stationary phase (i.e. not growing)?

Answer 15

They are more difficult to treat with antibiotics

Question 16

What are spores?

Answer 16

High resistant structures that are formed by some bacteria

Question 17

Why are spores highly resistant?

Answer 17

Because the bacteria are in the stationary state of growth, and are encapsulated in a tough coat

Question 18

Where can bacteria grow?

Answer 18

• Agar
• Broth
• Biofilms

Question 19

What do bacteria form when growing in agar?

Answer 19

Colonies

Question 20

When can bacteria form biofilms?

Answer 20

In natural environments

Question 21

Draw a diagram illustrating biofilm formation

Answer 21

Question 22

What must bacteria have to grow?

Answer 22

• A suitable energy source
• Specific building blocks for growth
• Specific atmosphere

Question 23

What specific building blocks for growth do bacteria need?

Answer 23

• Carbons
• Nitrogen
• Water
• Trace elements

Question 24

What is the growth and survival of microbes very important in?

Answer 24

Maintaining the transmission of infection and sustaining the reserviors of infectious agents

Question 25

When are organisms easier to eradicate?

Answer 25

When they can only survive and grow in humans

Question 26

Give an example of an organism that can only survive and grow in humans?

Answer 26

Smallpox

Question 27

When are organisms nearly impossible to eradicate?

Answer 27

When they have an environmental or animal reservior

Question 28

What determines the disease development spread of a microbe?

Answer 28

The rate at which they grow

Question 29

What kind of diseases have a rapid disease developement spread?

Answer 29

Those with acute onset

Question 30

What is crucial with diseases witha rapid disease development spread?

Answer 30

Early diagnosis

Question 31

Give an example of a disease with rapid disease development spread

Answer 31

Neisseria meningitides

Question 32

What kind of diseases have a slower disease development spread?

Answer 32

Those that are slowly progressing

Question 33

What is the result of a disease having a slower disease development spread?

Answer 33

Urgent diagnosis is not as crucial for the patient

Question 34

Give an example of a disease with a slower disease development spread

Answer 34

Mycobacterium tuberculosis causing TB

Question 35

What is the latent period in the growth of a microbe?

Answer 35

The time between first initial infection and presentation of symptoms

Question 36

What are the main ways that bacteria can develop antibiotic resistance?

Answer 36

* Intrinsic resistance * Extrinsic resistance

Question 37

What happens in intrinsic resistance?

Answer 37

The bacteria undergo a genetic mutation within their own genetic information to develop a means of becoming resistant to a specific or group of antibiotics

Question 38

What happens in extrinsic resistance?

Answer 38

The transfer of genetic material occurs between bacteria

Question 39

How can extrinsic resistance occur?

Answer 39

* Transformation * Conjugated * Trasduction

Question 40

What happens in transformation of bacteria?

Answer 40

Uptake of naked DNA and incorporation into their own genome

Question 41

What is the result of transformation of bacteria?

Answer 41

The bacteria now has the genes to develop the antibiotic resistance the original bacterium had

Question 42

What happens in conjugation of bacteria?

Answer 42

The bacteria can use plasmid DNA to develop antibiotic resistance

Question 43

What are plasmids?

Answer 43

Circular DNA structures found in the bacterial cytoplasm that can code for many genes, **including antibiotic resistance**

Question 44

What can bacterial conjugation cause?

Answer 44

Rapid spread of resistance amongst bacterial colonies

Question 45

What happens in transduction in bacteria?

Answer 45

Resistance genes are mobilised by the action of some bacteriophages

Question 46

By what mechanisms can bacteria have antibiotic resistance?

Answer 46

* Antibiotic modification * Impermeability * Efflux mechanisms * Alteration of the target site

Question 47

What are the types of antibiotic modification?

Answer 47

* Enzyme inactivation * Enzyme addition

Question 48

What happens in enzyme inactivation?

Answer 48

The organisms will produce enzymes that degrade the antibiotic and inactivates it

Question 49

Give an example of an enzyme that can degrade antibiotics?

Answer 49

ß-lactamase

Question 50

What does ß-lactamase do?

Answer 50

Breaks open the ß-lactam ring of penicillins and inactivates it

Question 51

What happens in enzyme addition?

Answer 51

The organism expresses an enzyme which can add a group to the antibiotic and inhibits its activity

Question 52

Give an example of antibiotic resistance by enzyme addition

Answer 52

Resistance to aminoglycosides by addition of acetyl or amino groups

Question 53

What is meant by impermeability? ## Footnote *With respect to bacterial resistance*

Answer 53

When the bacteria become resitant to antibiotics as their cell envelope is impermeable to particular antibiotics

Question 54

Give two examples of antibiotics where bacteria have become resistant through impermeability

Answer 54

* Pseudomonas spp. * ß-lactam

Question 55

Give an example of an efflux mechanism of antibiotic resistance

Answer 55

The bacteria can pump the antibiotic out of the cell by a newly coded for protein

Question 56

Give an example of a case of resistance by pumping antibiotics out of the cell by a newly coded for protein

Answer 56

E. Coli to tetracyclins

Question 57

What does alteration of the target site involve?

Answer 57

The alteration to the target that the antibiotic normally takes to become resistant to the antibiotic

Question 58

Give an example of bacterial resistance through alteration of the target site

Answer 58

Resistance to rafampicin, *which inhibits the ß-subunit of RNA polymerase,* where the RNA polymerase gene becomes altered to new RNA polymerase is not affected by rifampicin

Question 59

What must be done to medical equipment to reduce infection rates?

Answer 59

Remove the microbes that contaminate them on a daily basis

Question 60

What is sterilisation?

Answer 60

The inactivation of all self-propagating biological entities associated with the material or the area under consideration

Question 61

Why is sterilisation very hard to achieve?

Answer 61

Due to the presence of prions or spores

Question 62

What is used to sterilise surgical instruments in a clinical setting?

Answer 62

An autoclave

Question 63

What does an autoclave do to remove microorganisms?

Answer 63

Pressure and high temperature steam

Question 64

Other than an autoclave, how can surgical equipment be sterilised?

Answer 64

Radiation

Question 65

What is disinfection?

Answer 65

The removal of pathogenic organisms to a level where they no longer constitute a risk to individuals

Question 66

What is the advantage of disinfection over sterilisation?

Answer 66

It is much easier to achieve

Question 67

What is antisepsis?

Answer 67

Disinfection applied to human tissues

Question 68

How can disinfection be acheived?

Answer 68

* Physical processes * Chemical processes

Question 69

What physical processes can achieve disinfection?

Answer 69

* Filtration of air * Heat * Radiation

Question 70

What chemical processes can achieve disinfection?

Answer 70

Liquid or gaseous agents