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Year One - Principles of Disease > Bacteria > Flashcards

Bacteria Flashcards

1
Q

What are bacteria?

A

Micro-organisms that cause infectious disease

Single-celled prokaryotes

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2
Q

How do bacteria reproduce?

A

Binary fission

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3
Q

Describe the three membranes of bacteria.

A

Bacteria cells consist of three membranous layers; a capsule, a cell wall and an inner membrane.

The capsule is the outermost layer of the bacteria cell, not all bacteria have one.

The cell wall is the layer underneath, with the inner membrane being the innermost layer.

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4
Q

Describe the structure of bacteria.

A

Within the bacteria there is cytoplasm, ribosomes and a single chromosome. The chromosome is free within the cell as there is no nucleus present.

Flagellum - threadlike structure that enable them to swim.

Fimbria - a series of thread-like projections that can attach to their external environment.

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5
Q

What are the two types of bacteria?

A

Gram-positive

Gram-negative

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6
Q

What is the structural difference between gram-positive and gram-negative bacteria?

A

Gram-negative bacteria have an additional outer membrane that is composed of lipopolysaccharides and proteins.

Gram-positive bacteria have a thick peptidoglycan layers and gram-negative bacteria have a thin peptidoglycan layer

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7
Q

How do gram-positive bacteria appear in gram stain microscopy?

A

Purple

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8
Q

How do gram-negative bacteria appear in gram stain microscopy?

A

Red

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9
Q

Describe the steps involved in gram stain microscopy.

A
  1. Spread bacterial culture on a glass slide and fix the sample to the slide by heating it with a Bunsen flame.
  2. Add crystal violet, which all bacteria take up and all stain purple.
  3. Add iodine, which results in crystal violet complexes forming. These complexes form in all of the bacteria cells.
  4. Add acetone alcohol, which only decolourises gram-negative bacteria cells.
  5. Add a secondary solvent to the slide, which stains all the decolourised gram-negative bacteria cells red.
  6. Airdry the glass slide and view it under the microscope.
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10
Q

What are the advantages of gram stain microscopy?

A

Quick - early indication of bacteria causing infection and we can prescribe an effective antibiotic

Simple

Inexpensive

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11
Q

What are the two shapes of bacteria?

A

Cocci (spherical)

Bacilli (rod)

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12
Q

What do the cell walls of bacteria consist of?

A

Plasma membrane, which contains a cross link of penicillin binding proteins. These proteins allows passage of molecules across the cell wall.

Above plasma membrane there is a peptidoglycan layer, which adds strength and shape. Thicker in gram-positive than gram-negative

ONLY gram-negative bacteria contain an outer membrane, which is made up lipopolysaccharides and penicillin binding proteins. Lipopolysaccharides allow a strong immune response

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13
Q

What is the periplasm space?

A

The space in gram-negative bacteria between the inner and outer membrane in the ell wall.

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14
Q

What are the two types of capsules?

A

Rigid

Slimy

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15
Q

What is the role of a capsule?

A

Preventing phagocytosis and allowing them to evade the immune response

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16
Q

What are the four types of flagellum?

A

Type A - consists of one single flagella

Type B - consists on multiple flagella, all on the same side

Type C - consists of two flagella, one on either side

Type D - consists of multiple flagella all over

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17
Q

What structure in bacteria allow biofilm formation?

A

Fimbriae, as they are Abel to attach to other bacteria cells and pull them together to form a community

18
Q

What is biofilm formation?

A

A community of bacteria.

19
Q

What are spore-forming bacteria? What are spores?

A

Bacteria that form spores.

Spores are the dormant form of bacteria and are highly resistant to physical and chemical influences, allowing them to live for a long period of time

20
Q

What are streptococci bacteria?

A

Chained cocci bacteria

21
Q

What are staphylococci bacteria?

A

Clustered cocci bacteria

22
Q

How do we classify between streptococci gram positive bacteria?

A

Haemolyse test

23
Q

What streptococci gram-positive bacteria partially haemolyse? What effect do they have on agar?

A

Alpha

Turn agar green

24
Q

What streptococci gram-positive bacteria completely haemolyse? What effect do they have on agar?

A

Beta

Turn agar clear

25
Q

What effect do streptococci non-haemolytic bacteria have on agar?

A

No effect

26
Q

How do we classify between staphylococci gram positive bacteria?

A

Coagulase test

27
Q

What is staphylococcus aureus? What features do they have?

A

Gram-positive bacteria.

Usually penicillin resistant due to its production of penicillinase. There are methicillin resistant Staph aureus (MRSA) and they pose major problems for infection, prevention and control in hospitals

28
Q

What is staphylococcus epidermis?

A

Gram-positive bacteria

29
Q

What is staphylococcus pneumoniae? What do they cause?

A

Gram-positive bacteria

Cause pneumonia, meningitis and septicaemia.

30
Q

What is streptococcus pyogenes? What features do they have? What do they cause?

A

Gram-positive bacteria

Beta-haemolytic

Group A streptococci

Cause pharyngitis, cellulitis and necrotising fasciitis.

31
Q

What are clostridium difficile? What do they cause? How can we detect it?

A

Gram-positive bacteria

Cause diarrhoea and colitis, due to the fact that they produce toxins.

Fatal if spread via spores

Increased risk of infection of these bacteria if you take antibiotics or anything else that disrupts normal gut flora

Antigen and toxin ELISA techniques on stool sample

32
Q

What are Escherichia coli? What feature do they have? What do they cause? Why are they virulent?

A

Gram-negative bacteria

All ferment lactose

UTI

Structure and toxins that they produce

33
Q

What two strains of E.coli cause diarrhoea?

A

Enterotoxigenic E. coli

Enterohaemorrhagic E. coli

34
Q

What are salmonella spp.? What feature do they have?

What do they cause?

A

Gram-negative bacteria

Don’t ferment lactose

Diarrhoea and enterocolitis

35
Q

What are campylobacter spp.? What feature do they have? How are they spread?
What do they cause?

A

Gram-negative bacteria

Microaerophilic - like low oxygen levels.

Spread through domestic chickens and animals

Diarrhoea - bloody, foul-smelling

36
Q

What are helicobacter pylori? What are they found?

What do they cause?

A

Gram-negative bacteria

Stomach where they damage mucosa and cause stomach ulcers

Gastric adenocarcinoma

37
Q

What are haemphilus influenzae?

What do they cause?

A

Gram-negative bacteria

Respiratory tract infections and meningitis in children

38
Q

What are bacteriodes?

What do they cause?

A

Gram-negative bacteria

Intra-abdominal abscesses and spread to other sites within the body to cause other abscesses

39
Q

What are miscellaneous bacteria?

A

Those that cannot be stained or cultured by standard methods.

40
Q

Name three types of miscellaneous bacteria.

A

Mycobacterium

Spirochaetes

Chlamydia

41
Q

How can we identify miscellaneous bacteria?

A

Special stains, such as Ziehl-Neelsen or Auramine.

Automated liquid cultures

Year One - Principles of Disease (15 decks)

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