2. Infection Model

Question 1

Outline the basic structure of a virus.

Answer 1

Nucleic acid (DNA or RNA) with a protein capsid coat
Envelope - lipid bilayer
'Spikes' on the outside to aid attachment and entry into host cells.

Question 2

Give an example of a common virus and its structure.

Answer 2

Adenovirus.

DNA, non -enveloped, icosahedral.

Question 3

What are bacteriophages?

Answer 3

Viruses that infect bacteria and are able to transmit DNA between bacteria.

Question 4

What are the 2 main bacterial shapes?

Answer 4

Cocci

Bacilli/rod-like

Question 5

What is a bacterial capsule commonly made up of?

Answer 5

Polysaccharide

Question 6

How can a bacterial capsule act as a virulence factor?

Answer 6

Poor immunogen - evades immune system and protects from phagocytosis.

Question 7

What colour do gram-positive bacteria stain?

Answer 7

Purple

Question 8

What colour do gram negative bacteria stain?

Answer 8

Pink

Question 9

What is the main structural differences in the cell wall structure of gram positive and gram negative bacteria?

Answer 9

Gram positive have a thick outer peptidoglycan layer.

Gram negative have thin peptidoglycan inner layer.
Lipopolysaccharide on the outside.

Question 10

What is lipopolysaccharide?

Answer 10

Virulence factor on the cell wall of gram negative bacteria.

Highly toxic and triggers inflammatory response.

Question 11

What is an aerobe and an obligate aerobe?

Answer 11

Bacteria that can survive in the presence of oxygen.

Obligate aerobes have an absolute requirement for oxygen.

Question 12

What is an anaerobe and an obligate anaerobe?

Answer 12

Anaerobes can survive in the absence of oxygen. Obligate anaerobes must have an oxygen-free environment to survive.

Question 13

Give an example of an anaerobe.

Answer 13

Clostridium difficile

Question 14

Are spores active or dormant?

Answer 14

Dormant form of the bacteria

Question 15

What is an exotoxin?

Answer 15

Toxin that is released from the bacteria to cause host damage.

Question 16

What is an endotoxin?

Answer 16

Toxin that is part of the bacterial structure and is only released during cell breakdown.

Question 17

Give an example of an endotoxin.

Answer 17

LPS

Question 18

Give an example of a virulence factor that aids adherence to host cells.

Answer 18

Pili

Question 19

Give an example of a yeast fungi.

Answer 19

Candida albicans

Question 20

How many cells are yeast fungi made up of?

Answer 20

1 (single-celled!)

Question 21

Which 2 pathogens are eukaryotes?

Answer 21

Fungi

Parasites

Question 22

Virus’ and bacteria are _________.

Answer 22

prokaryotes

Question 23

Give examples of patient factors in the infection model.

Answer 23

• Age
• Gender
• Social factors
• Physiological state
• Pathological state

Question 24

Why is place an important patient factor?

Answer 24

Current - local infections and outbreaks

Recent travel history

Question 25

Why does pathogen interaction with the host defences result in host damage?

Answer 25

Causes inflammation. interaction with cells such as neutrophils releases ROS and cytokines which can trigger local and systemic inflammatory response and host damage.

Question 26

What are the categories of treatment?

Answer 26

Supportive | Specific

Question 27

Give examples of commensal bacteria which is found on the skin.

Answer 27

Staphylocuccus aureus Staph. epidermidis Streptococcus species

Question 28

What infections does adenovirus commonly cause?

Answer 28

Conjunctivitis Respiratory treat infections Gastroenteritis

Question 29

What method could be used to identify adenovirus?

Answer 29

Viral PCR

Question 30

How is adenovirus usually transmitted?

Answer 30

Inhaled - easily spread in large groups

Question 31

What is the treatment for adenovirus?

Answer 31

Supportive as no anti-virals available.

Question 32

Outline the steps involved in gram-staining.

Answer 32

1. Crystal violet 2. Rinse, add Iodine 3. Rinse iodine, decolonize with acetone. 4. Rinse, apply counterstain safranin

Question 33

Why do gram positive organisms appear purple yet gram negative appear red?

Answer 33

Gram positive organisms retain the crystal violet stain due to the thick peptidoglycan layer. Gram negative organisms do not retain this, so take up the red colour of the counterstain safranin.

Question 34

What are the benefits of the microflora in our bodies?

Answer 34

1. Compete with invading pathogens for nutrients and space 2. Some bacteria in bowel produce antimicrobials 3. Stimulus for immune development 4. In gut provide nutrients - Vit K

Question 35

How can microflora become harmful and pathogenic?

Answer 35

1. If they are displaced from their normal site and introduced to a n abnormal site. 2. Bacteria can convert commonly ingested food into carcinogenic derivatives in colon 3. Can overgrow in immunocompromised people

Question 36

Outline the structure of bacteria.

Answer 36

``` DNA - circular Extra DNA elements - plasmids which are replicable and transferrable No membrane-bound organelles No nucleus Cell membrane and wall Pili and flagella Ribosomes Capsule (sometimes) ```