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Phase 1 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What are the two primary shapes of viruses?

A

Spherical-icosahedral symmetry eg. human papillomavirus. Rod-helical symmetry eg. tobacco mosaic virus.

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2
Q

How do viruses diverge so rapidly?

A

RNA viruses require a special replicase, RNA-dependent RNA polymerase, to replicate the genomes. This enzyme makes a lot of errors that cannot be corrected and so leads to virus divergence. This divergence gives rise to epidemics and pandemics, allows viruses to jump species and gives rise to resistance to vaccines and therapies.

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3
Q

What is a pandemic?

A

A global disease outbreak eg. HIV/AIDS, or influenza.

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4
Q

What is an epidemic?

A

Infectious disease spread rapidly to many people eg. 2003 severe acute respiratory syndrome (SARS).

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5
Q

Describe a bacterium

A

Single-celled prokaryotes with characteristic cellular organisation. Reproduce by binary fission.

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6
Q

Gram negative cell walls

A

Gram -ve bacteria have a thin layer of peptidoglycan in their cell wall. Also have an outer membrane made from LPS. Do not stain with crystal violet.

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7
Q

Gram positive cell walls

A

Gram +ve bacteria have a thick layer of peptidoglycan and lipoteichoic acid in their cell well. It is anchored to the cell membrane by diacylglycerol. Stained by crystal violet.

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8
Q

Describe a gram stain.

A

Fixation- crystal violet stain-iodine treatment-decolourisation- counter stain (safranin). Gram +ve will stain purple and gram -ve will stain pink.

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9
Q

Common gram positive cocci

A

Staphylococcus aureus and streptococcus pneumoniae.

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10
Q

Common gram positive bacilli

A

Listeria monocytogenes and Corynebacterium diphtheriae.

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11
Q

Common gram negative cocci

A

Neisseria meningiditis

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12
Q

Common gram negative bacilli

A

Escherichia coli and salmonella species.

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13
Q

What are bacteriophages?

A

Viruses of bacteria that may also transfer genes.

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14
Q

What is transposition?

A

Involves the transfer of DNA sequences from one DNA molecule to another within a cell.

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15
Q

What are spores?

A

Vegetative forms of certain bacteria to enable viability under adverse conditions. For example, Bacillus species eg. anthrax. They are formed under deprivation or stress , when cells are unable to replicate.

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16
Q

What are endospores?

A

Abundant in soils and consist of nucleic acid, some cytoplasm and tough outer coat.

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17
Q

What is an endotoxin?

A

Lipopolysaccharide in the outer membrane of gram-negative bacteria. “Endotoxin lipid A” and “O antigen”. Elicits a strong immune response and can make patients appear septic.

18
Q

What is a superantigen?

A

Exotoxins liberated by certain gram-positive bacteria. Produced intracellularly and released as mature toxins on infection. eg. S. aureus. Causes massive immune stimulation, can cause non-specific polyclonal T-cell stimulation and Toxic shock syndrome.

19
Q

What is sepsis?

A

A physiological response to infection involving cytokine cascades, free radical production and vasoactive mediators.

20
Q

What is SIRS?

A

Systemic inflammatory response syndrome.

21
Q

What is severe sepsis?

A

Sepsis with evidence of organ hypoperfusion eg. hypoxaemia, oliguria, acidosis, cerebral dysfunction.

22
Q

What is septic shock?

A

Severe sepsis with hypotension despite fluid resuscitation or vasopressor/inotropic support.

23
Q

Define disinfection

A

Removal of most but not all viable microorganisms to safe levels.

24
Q

Define sterilisation

A

Killing or removing all microorganisms including transmissible agents. Physical or chemical.

25
Q

Define pasteurisation

A

Reduces total number of microorganisms in heat-sensitive products.

26
Q

Name some mosquito borne diseases

A

Malaria, Lympathic filariasis, Zika, yellow Fever, Dengue, West Nile Virus.

27
Q

What arthropod causes African trypanosomiasis?

A

Tsetse flies.

28
Q

What arthropod causes Leishmaniasis?

A

Sandflies.

29
Q

What is Praziquantel?

A

Drug of choice against schistosomiasis. Very selective, acts mostly on adult worms.

30
Q

How to treat a returning traveller?

A

Take a full travel history and refer to a specialist infectious diseases unit if in any doubt.

31
Q

How to treat a prospective traveller?

A

Assess the risks in region of destination. Offer advice on avoidance of disease, drug prophylaxis and necessary vaccination.

32
Q

What is affinity maturation?

A

The process by which the affinity of antibodies produced in response to a protein antigen increases with prolonged or repeated exposure to that antigen. Occurs in the germinal centres of lymphoid follicles.

33
Q

Coccus

A

round (berry)

34
Q

Bacillus

A

rod

35
Q

Spirillum

A

spiral shaped

36
Q

Aureus

A

Golden

37
Q

Albus

A

white

38
Q

Staphylo

A

grape like (clusters)

39
Q

Strepto

A

twisted chain

40
Q

How can DNA be transferred naturally between bacteria?

A

Conjugation refers to direct transfer of DNA between bacterial cells in contact with each other - e.g. a plasmid conferring antibiotic resistance.

Phase 1 (13 decks)

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