Classification, identification of bacteria of medical importance Flashcards

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1
Q

What is microbiology?

A

The study of microscopic organisms

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2
Q

Name the two scientist who came up with the germ theory of disease

A

Louis pasteur and Heinrich Hermann Robert Koch

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3
Q

Name the three types of microorganisms

A
  1. Eukaryotes
  2. Prokaryotes
  3. Viruses
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4
Q

Name the most abundant micro organism on earth

A

Bacteria

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5
Q

Name the two types of bacterial cell structure

A

Gram positive

Gram Negative

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6
Q

Describe the structure of gram negative bacteria

A

They have a thin cell wall surrounded by a phospholipid membrane

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7
Q

How do we study bacteria

A

We need to isolate them in a pure culture

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8
Q

Can all bacteria be cultured

A

No as we can’t re create the environment for some bacteria to grow

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9
Q

State different initial characteristics we look at when studying bacteria

A
  1. Colony morphology

2. Cell morphology

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10
Q

What can we look at when studying bacterial colony morphology

A

1, Shape

  1. Haemolysis
  2. Pigment
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11
Q

Name the 3 categories we can put bacteria in when looking at haemolysis

A
  1. Alpha haemolysis
  2. Beta haemolysis
  3. Gamma haemolysis
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12
Q

What is alpha haemolysis?

A

A partial or “green” hemolysis associated with reduction of red cell hemoglobin.

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13
Q

What is beta haemolysis?

A

complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent

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14
Q

What can we look at when studying bacterial cell morphology

A
  1. Shape
  2. Spores
  3. Gram stains
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15
Q

How do we carry out gram staining

A
  1. Fixation : isolate a colony and place it on a glass slide
  2. Flood the surface of the glass slide with Crystal violet
  3. Rinse
  4. Flood the surface of the glass slide with Iodine
  5. Gram negative will Decolourise and the gram positive will turn purple
  6. Counter stain to identify gram negative
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16
Q

Following a Gram staining what colour will gram positive bacteria be?

A

Purple/ violet

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17
Q

Following a Gram staining what colour will gram negative bacteria be?

A

Pink

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18
Q

List differential characteristics we can look at when studying bacteria

A
  1. Metabolic activities
  2. Antigens
  3. Cellular composition
  4. DNA
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19
Q

How do we describe a bacterias metabolic activities?

A
  1. Fermentations
  2. Gas or gas production
  3. Enzymes
  4. utilisation of carbohydrates and proteins
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20
Q

Name some Molecular techniques we can use to look at bacterial DNA

A
  1. PCR
  2. Nucleic acid sequences
  3. Homology
  4. Probes
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21
Q

Name different tests we use to classify bacteria

A
  1. The Ziehl-Neelsen stain
  2. Catalase test
  3. Coagulase test
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22
Q

What is another name for the Ziehl-Neelsen stain ?

A

The acid fast stain

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23
Q

What do bacterial cell walls contain high concentration of?

A

Lipid

24
Q

Name the 3 steps of the Ziehl-Neelsen stain

A
  1. Staining using carbon fuchsin (pink)
  2. Decolorisation
  3. Staining using methyl blue (blue)
  4. Oxidase test
25
Q

How do we carry out the catalase test?

A
  1. Take a sample of a colony and place it onto an agar plate
  2. Make a smear of the colony into a glass slide
  3. Add hydrogen peroxide
  4. If the catalase enzyme is produced by the enzyme it will hydrolyse the hydrogen peroxide into H20
  5. This will show up as bubbles on the glass slide (catalase positive)
26
Q

What does the catalase test show?

A

If the bacteria in question produces the catalase enzyme

27
Q

What does the coagulase test show?

A

If the bacteria in question produces the coagulase enzyme

28
Q

Why do we carry out the coagulase test?

A

To see if the bacteria we are testing is staphylococcus aureus

29
Q

What is the oxidase test used to determine?

A

If the bacteria in question can produce cytochrome c oxidases

30
Q

How do we carry out the oxidase test?

A

We use tetra methyl para phenyl di amine

If it turns blue then the bacteria is oxidase positive

31
Q

Give examples of gram positive bacilli

A
  1. Mycobacterium tuberculosis,
  2. Mycobacterium leprae.
  3. M§ycobacterium avium-intracellulare
  4. Nocardia spp
32
Q

Give examples go spore producing gram positive bacilli

A
  1. Bacillus anthracis
  2. Bacillus cereus
  3. Clostridium spp
  4. Clostridium tetani
  5. Clostridium botulinum
33
Q

What does Bacillus anthracis cause?

A

Anthrax

34
Q

What does Bacillus cereus

A

Food poisoning

35
Q

What does Clostridium tetani cause?

A

Tetanus

36
Q

What does Clostridium botulinum cause?

A

Botulism

37
Q

Give examples of motile and non sporing bacilli

A

Listeria spp eg Listeria monocytogenes

38
Q

Where is Listeria monocytogenes found and what does it cause?

A

In foods such as cheese and pâtés, it causes listeriosis.

39
Q

Give examples of non motile and non sporing bacilli

A
  1. Corynebacteria
  2. Propionibacteria
  3. Lactobacilli
40
Q

What does Corynebacteria cause?

A

diphtheria

41
Q

What does Propionibacteria cause?

A

Acne

42
Q

Give examples of gram positive cocci

A
  1. staphylococci

2. streptococci

43
Q

Give examples of gram negative cocci

A
  1. Veillonella spp
  2. Parvobacteria
  3. acinobacters
  4. Neisseria spp.
  5. Neisseria spp.
44
Q

What do Neisseria spp cause?

A

meningococcal meningitis

45
Q

Give examples of gram negative bacilli

A
  1. Haemophilus spp.
  2. Legionella spp.
  3. Bordetella spp.
46
Q

What do Haemophilus spp cause?

A

associated with respiratory infections

May also cause epiglottitis

47
Q

What can Legionella pneumophila cause

A

Can cause Legionaire’s disease

48
Q

What can Bordetella spp.

A

Bordetella pertussis causes whooping cough.

49
Q

Give examples of gram negative bacilli

A
  1. Escherichia coli
  2. Yersinia pestis
  3. Shigella dysenteriae
  4. Salmonella spp.
  5. Providencia spp.
50
Q

What did Yersinia pestis cause?

A

Plague

51
Q

What is Shigella dysenteriae responsible

A

Responsible for bacterial dysentery

52
Q

What can Salmonella enterica

cause

A

gastroenteritis

53
Q

What can Salmonella typhi cause?

A

Typhoid fever

54
Q

What can Providencia spp cause

A

Members of this genus cause urinary tract infections

55
Q

What can Campylobacter spp cause

A

Bacterial diarrhoea

56
Q

What can Brucella spp cause

A

brucellosis (“undulant fever”).