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Year 2 EMS MoD > Introduction to Microbiology > Flashcards

Introduction to Microbiology Flashcards

1
Q

What is an akaryote?

A

A cell without a nucleus.

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2
Q

What is a prokaryote?

A

A single-celled organism that lacks a membrane-bound nucleus, mitochondria and other membrane-bound organelles.

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3
Q

What is a eukaryote?

A

An organism with DNA contained in chromosome in a distinct nucleus.

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4
Q

What proportion of the cells in the human body are not of human origin?

A

Over 90%.

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5
Q

What are the cells in the human body that are not of human origin called?

A

Commensal flora/microbiota.

  • mainly bacteria
  • some fungi/protista
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6
Q

Why are viruses not described as human commensal flora?

A

They don’t have a cellular structure, and can only infect host cells.

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7
Q

What is the main type of bacteria found on teeth?

A

Streptococcus mutans.

-commensal, but also causes disease

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8
Q

What is the main type of bacteria found on the tongue?

A

Streptococcus salivarius.

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9
Q

What is responsible for the initiation of ‘dental caries’, and what is the main risk factor?

A

Streptococcus mutans.

-high sugar diets

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10
Q

Are most microorganisms beneficial or harmful?

A

Most are beneficial.

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11
Q

What is responsible for providing most of the vitamin K we require?

A

Gut commensals.

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12
Q

Who set out the criteria to decide whether bacteria cause disease?

A 
Robert Koch (1834-1910).
-Koch's postulates
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13
Q

What does Koch’s postulates state? (4)

A

Causative organism must:

  • be isolated from every individual
  • be artificially cultivated
  • lead to symptoms
  • be recovered from individuals infected experimentally
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14
Q

What does Koch’s postulate state for viruses?

A
  • The gene should be present in a virulent strain, but not in a virulent strain
  • Antibodies against the gene should protect subjects
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15
Q

What are the main problems of Koch’s postulates?

A
  • Difficult to isolate causative agents
  • Impossible to culture some pathogens
  • Ethics - animal models not sufficient
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16
Q

Give an example of a bacterium that is difficult to isolate.

A

Mycobacterium tuberculosis.

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17
Q

Give an example of a bacterium that cannot be cultured.

A

MYCOBACTERIUM LEPRAE
-except in armadillos due to low body temperature
TREPONEMA PALLIDUM
-causes syphilis

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18
Q

What different illnesses does Salmonella typhi cause in mice and humans?

A

MICE - gastroenteritis

HUMANS - typhoid fever

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19
Q

What different illnesses does Salmonella typhimurium cause in mice and humans?

A

MICE - fatal infection similar to typhoid fever

HUMANS - gastroenteritis

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20
Q

What type of parasites are viruses?

A

Intracellular parasites.

-rely upon other cells for replication

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21
Q

What is the general structure of a virus?

A

Nucleic acid core surrounded by a protein coat.

-some also have a lipid envelope

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22
Q

What can viruses infect?

A 
Every class of organism.
-including bacteria
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23
Q

What is the nucleic acid core in viruses made up of?

A

Either DNA or RNA.

-not both

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24
Q

What is unusual about retroviruses?

A

RNA genome&raquo_space; cDNA copy upon infection of the host cell using reverse transcriptase.

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25
Q

What makes up the protein coat on viruses?

A

Capsomeres.

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26
Q

What area of the body does the syncytial virus infect?

A

Respiratory tract.

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27
Q

What is the special class of virus that attacks bacteria?

A

Bacteriophage.

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28
Q

What type of virus infects plants?

A

Viroids.

-naked infectious RNA molecules

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29
Q

What type of viral protein is thought to cause spongiform encephalopathies?

A

Prions.

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30
Q

What type of organisms are fungi?

A

Eukaryotes.

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31
Q

What is the cell wall of most fungi made up of?

A

Chitin.

-polymer of N-acetyl glucosamine

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32
Q

Where else is chitin found?

A

Exoskeleton of arthropods.

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33
Q

Why are fungi no longer thought to be plants?

A

Their cell walls are composed of chitin, not cellulose.

34
Q

What are moulds?

A

Multicellular fungi.

-grow into filaments (HYPHAE) that form mats (MYCELIA). May be subdivided by cross walls (SEPTA)

35
Q

What are the tiny filaments present in moulds called?

36
Q

What are the mats that forms from hyphae in moulds called?

37
Q

What type of fungus is common in bathrooms?

A

Cladosporium.

38
Q

What type of fungus is common in stale bread?

A

Penicillium.

39
Q

What are yeasts?

A

Unicellular fungi.

40
Q

What is the most common yeast in food production?

A

Sacharomyces cerevisiae.

-bread, alcohol, etc

41
Q

How do yeasts grow and multiply?

A

Budding daughter cells grow and multiply off mother cells.

42
Q

Give 2 examples of superficial infections caused by moulds.

A
  • Ringworm

- Athlete’s foot

43
Q

Give an example of an infection caused by yeast.

A

Thrush.

-candida albicans

44
Q

What are pseudomycelia?

A

A cellular association in bacteria and yeasts in which cells cling together in chains resembling small mycelia.
-e.g. candida albicans in thrush

45
Q

What type of organisms are protista?

A

Unicellular eukaryotes.

46
Q

What are the 4 classes of protista?

A
  • Apicomplexa
  • Flagellate protista
  • Ciliate protista
  • Amoeba
47
Q

What type of parasites are protista?

A

Intracellular and extracellular.

48
Q

How do protista spread?

A
  • Produce cysts&raquo_space; outside body
  • Insects
  • Sexual contact
49
Q

Give examples of infections caused by protista.

A 
Toxoplasmosis
Amoebic meningitis
Malaria
Leishmaniasis
Amoebic dysentery
Diarrhoea
50
Q

What types of protista cause diarrhoea? (2)

A
  • Giardia intestinalis

- Cryptosporidium spp. (associated with AIDS)

51
Q

What is Trichomonas vaginalis and what does it cause?

A

A protista, causes vaginal infections/discharge.

-can cause balanitis in males

52
Q

What is Pneumocystis jiroveci?

A

A fungi.

  • was thought to be a protista
  • causes pneumonia in people with AIDS
53
Q

What is the cell structure of bacteria?

A

Prokaryotes.

-lack membrane-bound nucleus

54
Q

What are the different shapes of bacteria?

A
  • Round (COCCI)
  • Rod-shaped (BACILLI)
  • Spiral
55
Q

How does gram staining differentiate between different types of bacteria?

A

Gram positive retain crystal violet dye when mixed with iodine&raquo_space; PURPLE.
Gram negative are decolourised by iodine&raquo_space; PINK.

56
Q

What is the envelope of Gram positive bacteria made of?

A
  • 30-40 layers of peptidoglycan
  • sugar and short peptides containing D-/L-amino acids
  • polymers (e.g. teichoic acid)
57
Q

What is the envelope of Gram negative bacteria made of?

A
  • Very little peptidoglycan (1-2 layers)

- Contains complex ‘outer membrane’

58
Q

What does the outer membrane of gram negative bacteria contain?

A

Lipopolysaccharide.

-form surface antigen with lipid A&raquo_space; endotoxin

59
Q

What does the lipid A on gram negative bacteria cause?

A

Gram negative shock.

60
Q

What makes bacteria mobile?

61
Q

What are fimbriae?

A

Hair-like structures surrounding gram negative bacteria.

-aid adhesion onto surfaces

62
Q

What are pili?

A

Tubes that join gram negative bacteria together during conjugation.
»exchange genetic material

63
Q

What structures are responsible for spreading antibiotic resistance between bacteria?

64
Q

What is the function of the capsule surrounding some bacteria?

A

Protect bacteria.

-even within phagocytes

65
Q

What is the function of the slime produced by some bacteria?

A

Helps them to stick to surfaces.

66
Q

What does the slime produced by Streptococcus mutans enable it to do?

A

Stick to the hard enamel on teeth.

-forms plaque and eventually dental caries

67
Q

Where do coagulase-negative staphylococci live, and what sorts of infections do some strands cause?

A

On the skin, and some produce slime that enable them to stick to plastics.
-infections associated with implanted plastic medical devices

68
Q

What are endospores?

A

Highly resistant structures produced by some bacteria that protect against heat and radiation.

69
Q

How are infections spread?

A
  • Airborne (droplets)
  • Faecal-oral
  • Sexual contact
  • Innoculation (e.g. IV)
  • Animals
70
Q

What infections are commonly spread by the faecal-oral route? (4)

A
  • Typhoid
  • Cholera
  • Dysentery
  • Hepatitis A
71
Q

What genus of protista causes malaria?

A

Plasmodium.

72
Q

What is zoonosis?

A

The transmission of disease from animals to humans.

73
Q

What is a fomite?

A

An inanimate object (e.g. pen) that is capable of transmitting infection.

74
Q

What are virulence factors?

A

Molecules produced by pathogens that enable them to colonise a niche in the host/complete the cycle of infection.

75
Q

What are intoxication illnesses?

A

Illnesses that can be caused from exposure to a toxin rather than a living organism.
-e.g. tetanus, botulism, ergotism

76
Q

What is another name for tetanus?

A

‘Lockjaw’.

-causes muscles to go into rigid spasm; face is affected first

77
Q

What are the 2 types of toxins produced by bacteria?

A

Exotoxins and endotoxins.

78
Q

What is the difference between endotoxins and exotoxins?

A

ENDOTOXINS - stored in bacterial cells and released when they disintegrate.
EXOTOXINS - secreted by bacterial cells.

79
Q

What is the effect of some bacteria producing soluble antigens?

A

May combine with antibodies&raquo_space; circulating immune complexes and become trapped in vessels.
-e.g. glomerulonephritis

80
Q

What bacteria causes glomerulonephritis and rheumatic fever?

A

Streptococcus pyogenes.

81
Q

How do bacteria cause disease?

A
  • Intoxication
  • Toxin production (endo-/exo-toxins)
  • Attachment (pili/fimbriae)
  • Aggressin production
82
Q

What are dental caries?

A

AKA tooth decay.

-break down of teeth due to bacterial activity

Year 2 EMS MoD (20 decks)

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