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MCD Medicine > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What colour do gram positive bacteria stain?

A

Purple

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2
Q

Describe the structure of gram positive and gram negative bacteria

A

Gram positive: No outer membrane, thick peptidoglycan layer

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

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3
Q

List three examples of gram positive bacteria

A

Streptococcus pneumoniae, Staphlococcus aureus, streptococcus pyogenes

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4
Q

List three examples of gram negative bacteria

A

Salmonella, Shigella, E.coli

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5
Q

What 5 bacteria must a bacteria have to be pathogenic?

A
  1. Colonise
  2. Persist
  3. Replicate
  4. Disseminate
  5. Cause disease
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6
Q

What is the type III secretion system?

A

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

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7
Q

How are accessory genes acquired?

a) Horizontal transfer
b) Vertical transfer

A

a) horizontal transfer: transformation, conjugation and transduction

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8
Q

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

A

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

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9
Q

What factors effect the infectious dose?

A
  1. Route of transmission
  2. Ability to colonise
  3. Tropism and motility
  4. Replication speed
  5. Immune evasion
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10
Q

What is an antibiotic?

A

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

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11
Q

What is the minimum inhibitory concentration?

A

The lowest concentration of antibiotic required to inhibit growth

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12
Q

Name 3 mulit-resistant bacteria

A
  1. Pseudomonas aeruginosa
  2. S. aureus
  3. E.coli
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13
Q

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

A

Tetracycline

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14
Q

How does the beta lactam class of antibiotics act?

A

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

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15
Q

Chloramphenicol:

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

A

a) Halt protein synthesis

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

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16
Q

List the four methods bacteria can use to develop antibiotic resistance

A
  1. Altered metabolism
  2. Decreased drug accumulation
  3. Altered target site
  4. Inactivation of antibiotic
17
Q

List three examples of non genetic mechanisms of acquiring antibiotic resistance

A
  1. Spores
  2. Biofilms
  3. Slow growth
    (4. Persisters)
18
Q

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

A
  1. overcrowded hospitals
  2. indwelling devices e.g. intubation
  3. broken skin e.g. surgical wound
19
Q

How can we prevent the emergence of AB resistance?

A

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

20
Q

Name the three types of disease caused by fungal infection

A
  1. Allergy
  2. Mycotoxicoses
  3. Mycoses
21
Q

What is mycotoxicoses?

A

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

22
Q

What are the 4 different types of mycoses?

A
  1. Superficial
  2. Cutaneous
  3. Subcutaneous
  4. Systemic/deep
23
Q

Which of the following is the most common paediatric dermatophyte?

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

A

b) Tinea capitis = ringworm of the scalp

24
Q

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

A

TRUE!

25
Q

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

A
  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
26
Q

What does caspofungin target?

A

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

27
Q

What is a virus?

A

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

28
Q

Does Influenza virus have an RNA or DNA genome?

A

RNA (-)

29
Q

What is syncytia?

A

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

30
Q

What are the three phases of growth of a virus?

A
  1. Eclipse phase
  2. Logarithmic phase
  3. Cell death
31
Q

How can you diagnose a viral infection?

A

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

32
Q

Name two viruses we have no permissive cell lines for?

A

Norovirus and Hep C

33
Q

What type of viral vaccine is given for measles:

a) Live attenuated
b) Fractionated
c) Inactivated

A

a) Live attenuated

34
Q

Give an example of a subunit vaccine

A

Hepatitis B

35
Q

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

A

Large progeny, short replication time and high mutation rates

36
Q

What is antigenic drift?

A

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

37
Q

What are the risk factors for dengue haemorrhagic virus?

A

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

38
Q

Dengue antibodies:

a) Enhance infection
b) Neutralise infection
c) both

A

c) they can do both

MCD Medicine (4 decks)

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