Microbiology

Question 1

What colour do gram positive bacteria stain?

Answer 1

Purple

Question 2

Describe the structure of gram positive and gram negative bacteria

Answer 2

Gram positive: No outer membrane, thick peptidoglycan layer

Gram negative: Two membranes (inner and outer), smaller peptidoglycan later

Question 3

List three examples of gram positive bacteria

Answer 3

Streptococcus pneumoniae, Staphlococcus aureus, streptococcus pyogenes

Question 4

List three examples of gram negative bacteria

Answer 4

Salmonella, Shigella, E.coli

Question 5

What 5 bacteria must a bacteria have to be pathogenic?

Answer 5

1. Colonise
2. Persist
3. Replicate
4. Disseminate
5. Cause disease

Question 6

What is the type III secretion system?

Answer 6

It is used by GRAM NEGATIVE bacteria to invade host cells and deliver virulence proteins. It is used by Salmonella to invade epithelial cells.

Question 7

How are accessory genes acquired?

a) Horizontal transfer
b) Vertical transfer

Answer 7

a) horizontal transfer: transformation, conjugation and transduction

Question 8

What is pathogenicity and what are the two factors that affect it?

Answer 8

Pathogenicity is the ability of an organism to cause disease
Two factors: Infectivity and virulence

Question 9

What factors effect the infectious dose?

Answer 9

1. Route of transmission
2. Ability to colonise
3. Tropism and motility
4. Replication speed
5. Immune evasion

Question 10

What is an antibiotic?

Answer 10

=An antimicrobial agent produced by a microorganism that kills or inhibits other micro-organisms

Question 11

What is the minimum inhibitory concentration?

Answer 11

The lowest concentration of antibiotic required to inhibit growth

Question 12

Name 3 mulit-resistant bacteria

Answer 12

1. Pseudomonas aeruginosa
2. S. aureus
3. E.coli

Question 13

Which class of antibiotics works by binding the 16s component of the 30s ribosomal subunit and inhibiting protein synthesis?

Answer 13

Tetracycline

Question 14

How does the beta lactam class of antibiotics act?

Answer 14

They prevent the synthesis of peptidoglycan by binding to the penicillin binding proteins.

Question 15

Chloramphenicol:

a) Halt protein synthesis/translation
b) Stop bacterial wall synthesis
c) Interfere with bacteria transcription
d) Prevent replication of the bacterial DNA

Answer 15

a) Halt protein synthesis

they bind to the 50s ribosomal subunit and block peptidyl transfer

Question 16

List the four methods bacteria can use to develop antibiotic resistance

Answer 16

1. Altered metabolism
2. Decreased drug accumulation
3. Altered target site
4. Inactivation of antibiotic

Question 17

List three examples of non genetic mechanisms of acquiring antibiotic resistance

Answer 17

1. Spores
2. Biofilms
3. Slow growth
   (4. Persisters)

Question 18

Name three factors that can increase your risk of developing a hospital acquired infection

Answer 18

1. overcrowded hospitals
2. indwelling devices e.g. intubation
3. broken skin e.g. surgical wound

Question 19

How can we prevent the emergence of AB resistance?

Answer 19

Reduce use of broad spectrum antibiotic, close monitoring, combined therapy, quicker identification of resistant strains, prescribing strategies (e.g. tighter controls)

Question 20

Name the three types of disease caused by fungal infection

Answer 20

1. Allergy
2. Mycotoxicoses
3. Mycoses

Question 21

What is mycotoxicoses?

Answer 21

A toxic reaction caused by ingestion or inhalation of mycotoxins (secondary metabolites of mould)

Question 22

What are the 4 different types of mycoses?

Answer 22

1. Superficial
2. Cutaneous
3. Subcutaneous
4. Systemic/deep

Question 23

Which of the following is the most common paediatric dermatophyte?

a) Tinea peditis
b) Tinea capitis
c) Tinea corpotis
d) Tinea cruris

Answer 23

b) Tinea capitis = ringworm of the scalp

Question 24

More people die from the top 10 fungal diseases than of TB or malaria- True or false?

Answer 24

TRUE!

Question 25

What are the three targets for antifungals and give an example drug for each?

Answer 25

1. Cell membrane (ergesterol): azoles, e.g. fluconazole and polyene e.g. amphotericin B 2. DNA/RNA synthesis (pyrimidine analogues e.g. flucytosine) 3. Cell wall (glucan and chitin): Echinocandins e.g. Caspofungin

Question 26

What does caspofungin target?

Answer 26

Caspofungin targets the cell wall. Specifically it nonspecifically inhibits the beta 1,3 gluten synthase.

Question 27

What is a virus?

Answer 27

Infectious obligate intracellular parasite. They can be enveloped or non-eveloped

Question 28

Does Influenza virus have an RNA or DNA genome?

Answer 28

RNA (-)

Question 29

What is syncytia?

Answer 29

It is when viruses with surface proteins can fuse together at neutral pH

Question 30

What are the three phases of growth of a virus?

Answer 30

1. Eclipse phase 2. Logarithmic phase 3. Cell death

Question 31

How can you diagnose a viral infection?

Answer 31

Detect viral genome, viral antibodies, viral proteins. Detect cytopathic effect in cultured cells Detect antibodies produced against virus (serology)

Question 32

Name two viruses we have no permissive cell lines for?

Answer 32

Norovirus and Hep C

Question 33

What type of viral vaccine is given for measles: a) Live attenuated b) Fractionated c) Inactivated

Answer 33

a) Live attenuated

Question 34

Give an example of a subunit vaccine

Answer 34

Hepatitis B

Question 35

Why is viral evolution in response to selection pressure so fast?

Answer 35

Large progeny, short replication time and high mutation rates

Question 36

What is antigenic drift?

Answer 36

Mechanism for variation in viruses that involves the accumulation of mutations within the genes that encode for antibody binding sites

Question 37

What are the risk factors for dengue haemorrhagic virus?

Answer 37

Age, pre-existing antibodies, age, higher risk in secondary infections, higher risk in areas where two or more serotypes

Question 38

Dengue antibodies: a) Enhance infection b) Neutralise infection c) both

Answer 38

c) they can do both