Pathogens

Question 1

Why don’t we usually see bacteria on micrographs?

Answer 1

they stain poorly with H and E, the tissue preparation deliberately removes them or insufficient magnification

Question 2

What is a microbiome?

Answer 2

The collection of microbes usually present on a human. This will be dependent on the health of the human in question.

Question 3

What can we detect with Acid-Fast Stain?

Answer 3

The bacterial causes of tuberculosis and leprosy.

Question 4

How does Gram stain work and what are the results?

Answer 4

Positively charged crystal violet binds to negatively charged cell components. We attempt to extract the complex and then add red dye.
Red = gram negative
Purple = gram positive

Question 5

Why do some bacteria stain positive with Gram stain?

Answer 5

They have thicker peptidoglycan cell walls which prevent the extraction of the complexes of Gram stain.

Question 6

Name 3 ways that bacteria can grow

Answer 6

broth turbidity, colonies and biofilms

Question 7

What are the requirements for bacterial growth?

Answer 7

specific energy source, specific building blocks and specific atmosphere

Question 8

Name some Gram positive bacteria

Answer 8

staphylococci, streptococci and clostridium

Question 9

Name some Gram negative bacteria

Answer 9

Neisseria, Salmonella, Helicobacter, Pseudomonas, Legionella

Question 10

What are the differences between prokaryotes and eukaryotes?

Answer 10

P: 1 chromosome, no introns, 70S ribosomes, cell walls, coupled transcription and translation

E: many chromosomes, introns, 80S ribosomes, no cell walls, compartmentalised transcription and translation

Question 11

Where do most infections take place?

Answer 11

The epithelial tissue

Question 12

Define infection

Answer 12

The establishment of an organism on or in a host associated with its multiplication and damage to or dysfunction of the host specifically related to the organism or its products.

Question 13

How do viruses affect histology?

Answer 13

viral inclusion bodies (Negri bodies) and cytopathic effects

Question 14

What kind of nucleic acids do viruses contain?

Answer 14

RNA or DNA (But not both)

Question 15

Are enveloped or naked viruses harder to destroy?

Answer 15

Naked viruses

Question 16

Which processes do the viruses require hosts for?

Answer 16

energy generation, protein synthesis and nucleic acid synthesis

Question 17

What does it mean if the virus has +ssRNA?

Answer 17

The genomic RNA can serve as mRNA and be directly translated into protein.

Question 18

What does it mean if a virus has -ssRNA?

Answer 18

The genomic RNA cannot serve as mRNA and therefore cannot be directly translated into a protein.
This is because the sequence is the complementary sequence to the one we need for translation.

Question 19

If the virus contains RNA, what enzyme will be required for DNA synthesis?

Answer 19

Reverse transcriptase

Question 20

What is a nucleocapsid?

Answer 20

A protein coat which encloses and protects genomic material.

May be involved in attachment to host cells.

Question 21

What is the envelope made from?

Answer 21

A piece of host cytoplasmic membrane

Question 22

What is the capsid composed of?

Answer 22

Individual subunits called capsomers.

Question 23

What are the 2 basic capsid structures?

Answer 23

Icosahedral

Helical

Question 24

What are bacteriophages?

Answer 24

Complex viruses that are involved in transfer of drug resistance. They can inject DNA through cell walls.

Question 25

Which receptor does HIV bind to?

Answer 25

The CD4 receptor on T lymphocytes

Question 26

Define host range

Answer 26

The spectrum of host cells that the virus can successfully infect and replicate in.

Question 27

How do we classify viruses?

Answer 27

Baltimore Scheme

Based on the relationship between the viral genome and the mRNA used for translation.

Question 28

Name some enveloped DNA viruses

Answer 28

Hepatitis B
Herpes
Small pox

Question 29

Name some non-enveloped DNA viruses

Answer 29

Papilloma viruses (warts and cervical cancer)

Question 30

Name some enveloped RNA viruses

Answer 30

Rubella
HIV 
Influenza
Measles
Mumps

Question 31

Name some non-enveloped RNA viruses

Answer 31

Polio
Hepatitis A
Colds

Question 32

Name some cytopathic effects

Answer 32

syncytic formation - giant multinucleated cells formed by fusion of plasma membranes
And chromosomal damage

Question 33

What is damage in infections often due to?

Answer 33

Ineffective host responses rather than direct toxicity of the microbe

Question 34

What is a latent infection?

Answer 34

The organism is not eliminated from the body but there are no symptoms. Many things may lead to its reactivation.

Question 35

How are new virus particles formed?

Answer 35

They are assembled within the host cells and then released by budding off or during cell lysis.

Question 36

How can viruses spread in the body?

Answer 36

Via nerves and the blood