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Y1 - MCD > Microbiology - extra > Flashcards

Microbiology - extra Flashcards

1
Q

What is meant by an acid-fast microorganism?

A

Contains large amount of lipid substances (mycelia acids) in the cell wall that resist the normal Gram stain so that they appear weakly gram-positive or gram-variable. They resist the initial dye and retain carbon fuschin.

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2
Q

What are two examples of acid-fast pathogens?

A

Mycobacteria tuberculosis and mycobacteria leprae.

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3
Q

What is the outer membrane in gram-negative bacteria made up of?

A

Lipopolysaccharide (PAMP)

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4
Q

What are three examples of a gram-positive pathogen?

A

1) Staph. aureus
2) Strepto. pneumoniae
3) Strepto. pyogenes

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5
Q

What are five examples of gram-negative pathogens?

A

1) Neisseria
2) Shigella
3) E. coli
4) Salmonella
5) Vibrio cholera

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6
Q

What are the three mechanisms by which bacteria survive in cells?

A
  • Prevent fusion with lysosymes
  • Survive in phagolysosymes (although this is a harsh environment)
  • Escape into the cytoplasm by breaking down the vesicle
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7
Q

What is a necrotic infectious lion?

A

Cell death under the superficial layer.

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8
Q

Examples of bacteria that enter the URT?

A
  • Strepto. pneumoniae

- Neisseria meningitides

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9
Q

Examples of viruses that enter the URT?

A
  • Influenza
  • Rhinovirus
  • Measles/varicella zoster
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10
Q

Examples of intrinsic pathogens that enter the urogenital tract?

A
  • E.coli from the large intestine

- Candida

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11
Q

Examples of extrinsic pathogens that enter the urogenital tract?

A
  • Neisseria gonorrheae
  • Chlamydia
  • HIV/AIDS
  • Syphilis
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12
Q

What does cellulitis cause?

A

Red inflammation of the skin as the infection spreads across the skin.

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13
Q

What is virulence?

A

A measure of the degree of the disease that a pathogen causes.

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14
Q

What is infectivity?

A

An organism’s ability to infect the host. This does not mean that it necessarily causes a disease.

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15
Q

How does staphylococcus aureus work once in the cell?

A
  • Produces toxin called pneumolysin which destroys lung tissue
  • Produces super antigens that interfere with normal T cell function
  • Leukocyclins are produced, causing neutrophil death and abcess formation
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16
Q

What are the exceptions to antibiotics with resistance emerging soon after their introduction?

A

Vancomycin and erythromycin - weren’t used much as high toxicity.

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17
Q

How do aminoglycosides work?

A

Interfere with RNA proof-reading and protein synthesis, resulting in misfolded proteins and loss of function.

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18
Q

Examples of multi-drug resistant gram-positive pathogens?

A
  • MRSA
  • Streptococcus pneumoniae
  • Clostridium difficile
  • Mycobacterium tuberculosis
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19
Q

Examples of multi-drug resistant gram-negative pathogens?

A
  • E.coli
  • Neisseria gonorrhoea
  • Salmonella
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20
Q

What is used for multi-drug resistant infections as a last effort?

A

Linezolid, daptomycin and tigecycline.

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21
Q

What is a pathogenicity island?

A

Horizontally acquired DNA that contributes to the virulence of a pathogen.

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22
Q

Examples of an acute, persistent, latent-reactivating and slow viral infection?

A

Acute - influenza
Persistent - CMV or HIV-1
Latent reactivating - varicella zoster
Slow - HIV/AIDS

23
Q

What is a host range?

A

The number of different species that a virus can infect.

24
Q

What is ELISA?

A

Enzyme-linked immunosorbent assay. Measures antibodies, antigens, glycoproteins and proteins in biological samples. Used in HIV diagnosis and pregnancy tests.

25
Q

What is a tissue tropism?

A

The cells and tissues of a host that support growth of a particular pathogen.

26
Q

Examples of receptor-specific tropism?

A

HIV - the HIV virus receptor GP120 binds to CD4 cells and co-receptors CCR5 and CXCR4.

27
Q

Examples of non-receptor-specific tropism?

A

Influenza - host proteases.

28
Q

Why is rubella dangerous in pregnancy?

A

Infects foetal neuronal tissue causing deafness and several other severe birth defects.

29
Q

What are the two vaccines available for the polio virus?

A

SALK - older, need larger doses

SABINE - better but if given to the immunosuppressed it can result in a persistent infection

30
Q

What is a toxoid vaccine?

A

Made from a toxin that have been made harmless but still illicit an immune response.

31
Q

What does a recombinant attenuated vaccine normally have?

A

Mutated virulence gene or deleted virulence gene.

32
Q

What are M2 channel inhibitors?

A

Used for the treatment of influenza.

  • M2 channel activation due to low pH allows protons to flow into capsid, breaking down the bonds in the cell membrane, causing the virus to uncoat and spread into the cell.
  • M2 channel inhibitors prevent viral uncoating.
33
Q

What are two examples of M2 channel inhibitors?

A

Amantadine and rimantadine.

34
Q

What is a problem with M2 channel inhibitors?

A

These work by fitting into the channels and blocking them. However, a single point mutation will result in a conformational change in the end protein so that it no longer fits properly. Therefore, resistance is common. All influenza strains are now resistant to Amantadine.

35
Q

What is a downside to non-nucleoside reverse transcriptase inhibitors?

A

Reverse transcriptase has such a high error rate in the virus that emergence of resistance is rapid.

36
Q

Why are neuraminidase inhibitors preferable to M2 channel inhibitors?

A

They work against Influenza A and B not just A (M2).

37
Q

How do neuraminidase inhibitors work?

A

The influenza virus produces neuraminidase. It destroys sialic acid in cell membrane (initially allows virus to enter) which allows the virus to escape and colonise other cells. Neuraminidase inhibitors prevent the virus from leaving the cell so the infection can be contained.

38
Q

Examples of neuraminidase inhibitors?

A

Relenza and Tamiflu.

39
Q

What drugs (apart from interferons and ribavirin) are used to treat Hep C?

A 
Protease inhibitors (telaprivir and boceprivir). 
NS5A inhibitors prevent replication (daclastivir)
40
Q

What is the issue with using interferons?

A

They activate everything including fever and inflammation. So although the virus is being suppressed the patient may actually feel worse.

41
Q

What are the only exception to antigen drift?

A

Rhinoviruses (humans)

Pigs do not experience antigenic drift as they do not live long enough to be infected with the same pathogen twice.

42
Q

Why does antigenic drift occur?

A

Antigens will change over time due to the selective pressures exerted by antibodies.

43
Q

How are arboviruses spread and examples (3)?

A

Through mosquitos and ticks.

  • Dengue
  • Yellow fever
  • West Nile virus
44
Q

Why is climate change causing an increase in arboviruses?

A

Global warming will cause a more global distribution of mosquitos.

45
Q

What is the zoonotic vector for MERS?

A

Camels

46
Q

Why was SARS easier to contain than influenza?

A

Most contagious during symptomatic stage so easy to contain the virus.

47
Q

What is aflatoxin?

A

Most carcinogenic natural compound known produced by Aspergillus flavus. Causes liver cancer.
- Common in S.E Asia

48
Q

Example of a superficial and deep mycoses infection?

A

Superficial - dandruff (malassezia globosa)

Deep - Candida/aspergillus

49
Q

What do azoles target and give examples (2) ?

A

Ergosterol biosynthesis in the cell membrane.

  • Fluconazole
  • Itraconazole
50
Q

Give an example for an anti-fungal that inhibits nucleic acid synthesis?

A

Cryptococcus (pyrimidine inhibitor) - analogue.

51
Q

What is sepsis?

A

When an infectious insult triggers a localised inflammatory reaction that spills over to cause systemic symptoms.

Severe sepsis - organ failure or unexplained metabolic acidosis

52
Q

Explain pathophysiology of sepsis.

A
  • Immune response increases fluid leakage so reduced BP.
  • Temperature increases with fever so oxygen consumption increases.
  • Cells are not getting enough oxygen due to low BP so metabolic acidosis follows.
  • Cells lose the ability to maintain the Na/K pump so APs reduced and fluid leakage increases further.
  • Inflammatory mediators increase coagulation and inhibit fibrinolysis (endogenous anticoagulants)
  • Increases chance of microvascular thrombosis which can lead to organ failure
53
Q

Symptoms of sepsis?

A
  • Extremes in body temp
  • Tachycardia
  • Tachypnea
  • Leukocytosis

Y1 - MCD (38 decks)

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