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Phase 2a > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Define asymptomatic carriage

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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2
Q

What is unusual about chlamydia compared to other bacteria?

A

It can only grow inside a host cell

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3
Q

Put the following in average size order:

bacteria, protozoa, virus

A

from largest to smallest:

Protozoa

Bacteria

Virus

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4
Q

When do bacteria produce spores?

A

When they run out of nutrients

A spore will only germinate once conditions are suitable again

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5
Q

Define heat labile

A

Can be unfolded through heating

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6
Q

What is special about obligate intracellular bacteria

A

They may not be cultured on artifical media

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7
Q

What is a molliculite?

A

Bacteria that we can grow on artifical media WITHOUT cell walls

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8
Q

5 stages of viral replication

A
  1. Attachment to a specific receptor
  2. Cell entry - uncoating of virion within cell
  3. Host cell interaction + replication - transcription & translation
  4. Assembly of virion
  5. Release of new virus particles
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9
Q

Define protazoa

A

A single celled eukaryotes (have a nucleus)

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10
Q

Name of the adult form a protazoa

A

Trophozoite

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11
Q

5 major groups of trophozoites

A

Flagellate

Amoebae

Microsporidia

Sporozoa

Ciliates

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12
Q

Biological role of protazoa

A

Consumers of bacteria, algae, microfungi

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13
Q

4 spcies of malaria that cause disease?

A

Plasmodia falciparum

Plasmodia ovale

Plasmodia vivax

Plasmodia malariae

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14
Q

Give the 8 stages of the lifecycle of malaria

A
  1. Mosquito bites somebody with malaria → ingests gametocytes
  2. Gametocytes mature in the mosquitos gut, invade blood stream & move to salivary glands
  3. Mosquito bites somebody else & transfers sporozoites to this person
  4. Sporozoites infect hepatocytes
  5. Develops into a schizont which bursts & infects RBCs
  6. Within the RBC, plasmodium becomes a trophozoite
  7. The trophozoite develops into a schizont which ruptures and re-infects another RBC
  8. Some trophozoites develop into gametocytes which are taken up by mosquitos
  9. Process repeats
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15
Q

Malaria treatment

A

Complicated/severe malaria = IV artesunate

Mild = lots of options, treat what is failing

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16
Q

3 key attributes of a pathogen to cause disease

A

Infectivity

Virulence

Invasiveness

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17
Q

How do beta-lactams work?

A
  1. Disrupt peptidoglycan production
  2. By covalently binding to penicillin binding proteins (PBPs)
  3. Cell wall is disrupted & lysis occurs
  4. Hypo-osmotic & iso-osmotic environment
  5. Active only against rapidly multiplying organisms
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18
Q

4 subclasses of beta-lactams

A

Penicillins

Cephalosporins

Carbapenems

Monobactams

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19
Q

Do beta-lactams work better in destroying gram negative or gram positive bacteria?

A

Gram positive

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20
Q

4 majors types of antibiotic

A

Beta lactams

Inhibiting nucleic acid synthesis

Inhibiting protein synthesis

Inhibiting folate synthesis

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21
Q

What are we trying to achieve when giving antibiotics?

A

Giving the immune system time and support to deal with an infection

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22
Q

2 main strains of HIV that affect humans

A

HIV-1

HIV-2 (mainly confined to West Africa)

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23
Q

How many genes does HIV express?

A

10

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24
Q

What is the main characteristic of a lentivirus?

A

Characterised by long incubation periods

25
Q

Barriers to HIV-1 vaccine development?

A

Live attenuated or killed vaccines are deemed too risky for HIV

HIV-1 is highly variable

A succesful vaccine would need to provide protection against HIV acquisiton by different routes

26
Q

What does TasP stand for?

A

Treatment as prevention (usually refers to HIV)

27
Q

What does PreP refer to in terms of HIV

A

Pre-exposure prophylaxis

28
Q

What does U=U stand for in terms of HIV?

A

Undetectable = Untransmittable

29
Q

What enzyme does HIV use to replicate?

A

Reverse transcriptase

30
Q

What cell type does HIV replicate within?

31
Q

2 markers used to monitor HIV infection?

A

CD4 cell count

HIV viral load

32
Q

From point of infection with HIV, roughly how long does it take to develop symptoms?

33
Q

5 stages of HIV infection?

A
  1. Primary infection
  2. Acute HIV syndrome
  3. Clinical latency
  4. Opportunistic disease
  5. Death
34
Q

Describe clinical latency

A

In undiagnosed HIV:

  1. Immune system produces CD4 cells & pop. increases
  2. Viral load temporarily decreases
  3. However, CD4 pop. will begin to slowly decline → immunosuppression
  4. Until pt presents with constitutional symptoms & opportunistic infections
35
Q

Most common AIDS defining illness

A

Pneumocystis Pneumonia

36
Q

What does HAART stand for?

A

Highly active anti-retroviral therapy

37
Q

How does HAART work?

A

Usually 3+ antiretroviral drugs

Act on different points in replication cycle to suppress viral replication

38
Q

4 classes of drugs used in HAART?

A

Reverse transcriptase inhibitors

Fusion/entry inhibitors

Intergrase inhibitors

Protease inhibitors

39
Q

How does triple therapy have an advantage over monotherapy in terms of HIV drug resistance?

A

1 HIV mutation in every 2 new viruses produced

1-10 billion new virus particles each day

1-5 billion mutations per day

With monotherapy, the mutant has a higher survival advantage

40
Q

2 ways HIV develops drug resistance?

A

Non-adherence

Drug-drug resistance

41
Q

Give an example of drug-drug interaction that may lead to HIV drug resistance

A

If lansoprazole (proton pump inhibitor) is given to a patient who is on rilpivirine

Significant decreases in rilpivirine plasma concentrations occur due to gastric pH increase

Loss of therapeutic effect of rilpivirine → resistance

42
Q

Chains of purple cocci are seen on a gram film.

They appear as above when grown on blood agar.

They don’t grow near the optochin disc (not shown). These are probably:

    • Streptococcus pneumoniae
    • Staphylococcus epidermidis
    • Viridans Streptococci
    • Group A streptococci (S. pyogenes)
    • Neisseria meningitidis
A

Streptococcus pneumonia

43
Q

A pink colony is picked off this MacConkey plate and is found to contain pink staining bacilli with Gram’s staining.

Which organism is most likely

  • Shigella sonnei
  • Listeria monocytogenes
  • Neisseria meningitidis
  • Eschericia coli
  • Streptococcus pyogenes
A

Eschericia coli

(Yes. E coli is a lactose fermenting gram negative bacillus. Listeria (bacilli), and Steptococci (cocci) are gram positive (purple). Neisseria are gram negative cocci not bacilli. Shigella species are non lactose fermenting - colourless / pale white on MacConkey)

44
Q

Which of the following is Haemophilus influenzae NOT an important cause of?

  • Meningitis in pre-school children
  • Otitis media
  • Pharyngitis
  • Gastroenteritis
  • Exacerbations of COPD
A

Gastroenteritis

H influenzae is a gram negative ‘cocco-bacillus’ - a short pink rod responsible for many types of respiratory tract infection. It does not cause gastroenteritis.

45
Q

Which of these is NOT a means by which viruses cause disease?

  • direct destruction of host cells
  • cell proliferation and cell immortalisation
  • inducing immune system mediated damage
  • Endotoxin production
  • modification of host cell structure or function
A

Endotoxin production

46
Q

When diagnosing viral infections which is true?

  • The sample must come from a sterile site
  • Electron microscopy is most appropriate
  • A black charcoal swab maintains virus better
  • PCR results take a week or more
  • A detectable IgM in serum may be diagnostic
A

A detectable IgM in serum may be diagnostic

47
Q

Which is most accurate?The HIV virus envelope contains

  • RNA + capsid + DNA polymerase
  • DNA + capsid + RNA reverse transcriptase
  • DNA + p24 + RNA polymerase
  • RNA + capsid + RNA reverse transcriptase
  • RNA + gp120 + RNA polymerase
A

RNA + capsid + RNA reverse transcriptase

48
Q

Which pair is correct?

  • Toxoplasma = bacteria
  • Ringworm = helminth
  • Aspergillus fumigatus = mycobacteria
  • Falciparum malariae = filarial worm
  • Giardia lamblia = protozoa
A

Giardia lamblia = protozoa

(ringworm = misnomer, fungal infection)

49
Q

Mycobacteria vs Bacteria. Which are which?

  • Resist destaining by acid and alcohol
  • Cell wall contains lipoarabinomannan
  • They divide every 30-60 minutes
  • They usually withstand phagolysosomal killing
  • May cause meningitis
A

Mycobacteria

  • Resist destaining by acid and alcohol
  • Cell wall contains lipoarabinomannan
  • They usually withstand phagolysosomal killing

Bacteria:

  • They divide every 30-60 minutes
  • May cause meningitis
50
Q

Regarding antimicrobial resistance, is the following true or false?

It is spread by plasmid mediated gene transfer

51
Q

Regarding antimicrobial resistance, is the following true or false?

Spontaneous gene mutations do not occur

52
Q

Regarding antimicrobial resistance, is the following true or false?

MRSA refers to vancomycin resistant S. aureus

53
Q

Regarding antimicrobial resistance, is the following true or false?

Meropenem is effective against all gram negative bacteria

54
Q

Regarding antimicrobial resistance, is the following true or false?

Broad spectrum agents promote resistance in the gut microbiome

56
Q

A 34 year old gay man who has had prolonged diarrhoea now presents short of breath with a dry cough and hypoxia. His chest x-ray is shown. Which is most accurate?

  • This is bacterial pneumonia caused by pneumocystis jirovecii.
  • It is too early for a 4th generation HIV test to be positive
  • The CD4 T cell count will be between 500 and 750
  • Even if the HIV test is negative this man has AIDS
  • With appropriate therapy he has a good prognosis
A

With appropriate therapy he has a good prognosis

57
Q

Infection control: which is false? The five steps of hand hygiene are to wash hands

  • Before contact with patient
  • Before bodily fluid exposure
  • Before aseptic procedures
  • After contact with patient surroundings
  • After patient contact
A
  • Before contact with patient - true
  • Before bodily fluid exposure - false
  • Before aseptic procedures - true
  • After contact with patient surroundings - true
  • After patient contact - true
58
Q

A 21 year old complains of myalgia, sore throat and tiredness. He is febrile and has an enlarged spleen. Which is the best answer?

  • He has sepsis and needs broad spectrum antimicrobial therapy with cefotaxime
  • A charcoal throat swab will confirm the diagnosis
  • Tests show atypical lymphocytes and detectable EBV IgM in serum
  • PCR on a viral throat swab will confirm the diagnosis
  • This is a viral upper respiratory tract infection and doesn’t warrant investigation
A

Tests show atypical lympocytes and detectable EBV IgM in serum.

(This is consistent with acute infectious mononucleosis from EBV infection and typically leads to the development of atypical lymphocytes on a blood film and detectable IgM against EBV. None of the criteria for sepsis have been suggested in the clinical story. Although bacterial throat infections such as those from S pyogenes can be diagnosed with a charcoal swab, and acute viral respiratory infections can be diagnosed with PCR, neither cause enlarged spleens acutely. EBV can be detected with a viral PCR but it is often shed asymptomatically in the throat in people who have long since recovered, so not helpful for diagnosing an acute infection.)

Phase 2a (12 decks)

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