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Flashcards in Anaerobic infections Deck (75):
1

What is an anaerobic organism?

One that cannot survive in an oxygen environment

2

What is a facultative anaerobe?

One that can grow partially in small levels of oxygen, so is not a true anaerobic organism

3

Give two gram negative anaerobic bacillus'

  • Bacteriodes 
  • Fusobacterium

4

Give a gram negative anaerobic coccus

Veillonella

5

Give a gram positive anaerobic bacillus

Clostridium

6

Give a gram positive anaerobic coccus

Anaerobic streptococci

7

What are the clostridia species?

A spore forming Gram positive bacilli

8

Where are clostridia found?

In soil and water, but also ubiquitous as part of normal human microbiota

9

How many species of clostridia are there?

Around 80, but few that are disease causing

10

What does the clostridia pathophysiology involve?

Entering the anaerobic conditions as spores, germinating to form large numbers, and then releasing toxins to act as the main pathogenic factor

11

Where is clostridium difficile found?

In the human GI tract as microbiota

12

What % of the GI tract microbiota is clostridium difficle?

~3% in adults

13

Who has a higher % of clostridium difficile in the GI tract microbiota?

Children and neonates, and hospitalised patients

14

Why do hospitalised patients have more C. Difficile?

Because the use of broad-spectrum antibiotics will massively alter the GI microbiota, allowing for any endogenous C. Difficile to proliferate, or for an exogenous infection due to large numbers of patients releasing clostridium spores into the environment which can then colonise the GI tract

15

What does C. Difficile produce?

Two toxins;

  •  A
  • B

16

What do the A and B toxins produced by C. Difficile do?

Act on the gut to cause a mass release of cytokines

17

What does the release of cytokines due to C. Difficile cause?

Tissue damage and death, and the subsequent formation of a pseudomembrane

18

Why is it not a problem for neonates to carry large amounts of C. Difficile in their gut?

Because the lack of receptors for these toxins mean they can't take an effect

19

What do individuals infected with C. Difficile develop?

  • C. Difficile related diarrhoea
  • Abdominal pain
  • Malaise
  • Fever
  • Nausea

20

What can the inflammation from C. Difficile infection cause?

The stopping of bowel peristalsis

21

What can the stopping of bowel peristalsis related to C. Difficile lead to?

'Toxic megacolon'

22

What can toxic megacolon lead to?

Bowel perforation and septicaemia

23

How is diagnosis of C. Difficile made?

From a stool sample, checking for antigen detection or toxin detection

24

What does treatment of C. Difficile involve?

  • Oral metrinidazole or vancomycinD
  • iscontinuing of the current antibiotic regime if possible

25

What is vital to prevent the spreads of C. Difficile spores?

  • Hand-washing of health care workers
  • Individuals should be isolated in side rooms

26

Why must healthcare workers wash their hands to prevent the spread of C. Difficile?

Alcohol hand gel is ineffective against the spores

27

What is the main cause of gas gangrene?

Clostridium Perfringes

28

What kind of bacteria is clostridium perfringes?

Gram positive bacillus

29

Where is clostridium perfringes found?

As part of the intestinal microbiota, but its spores are found everywhere in the environment

30

Other than gas gangrene, what can clostridium perfringes cause?

Food poisioning

31

When can clostridium perfringes cause food poisioning?

When poorly cooked meats are consumed

32

What does gas gangrene develop from?

A devitalised wound

33

What is meant by a devitalised wound?

One with interruption to the blood supply

34

How does C. Perfringes cause gas gangrene?

The spores are taken in from the environment via the wound, and they germinate in the anaerobic wound and release toxins in the ischaemic conditions

35

What toxins are released by C. Perfringes?

Mainly α-toxins

36

What does gas gangrene cause?

Extensive damage to the surrounding soft tissue

37

Why is gas gangrene so named?

Gas slowly collects under the skin due to metabolising anaerobes

38

What does treatment of gas gangrene involve?

Debridement of the devitalised tissue and intravenous antibiotics

39

What antibiotics are given in gas gangrene?

Mainly penicillin

40

What is the causative agent for tetanus?

Colstridium tetani

41

What is the main symptom of tetanus?

Spastic paralysis

42

Where do tetanus infections occur?

In wounds deep enough to cause anaerobic conditions

43

What happens in a tetanus infection?

C. Tetani spores cause tetanospasmin

44

What does tetanospasmin do?

Prevents release of inhibitory transmitter γ-aminobutyric acid (GABA)

45

What is the result of tetanus induced GABA release inhibition?

Spastic paralysis at the site of injury

46

How can tetanus be diagnosed?

From history and clinical features

47

What does treatment of tetanus involve?

  • Muscle relaxant
  • Immunisation
  • Antibiotics

48

What are the types of vaccine for tetanus?

  • Active
  • Passive
  •  

49

What is given in active immunisation against tetanus?

Tetanus toxoid

50

What is given in passive immunisation against tetanus?

Human tetanus Ig

51

What causes botulism?

Clostridium botulinum

52

What is the main symptom of botulism?

Flaccid paralysis

53

Where is C. Botulinum widely distributed?

As a saprophyte in soil, food, etc

54

Why is C. Botulinum hard to get rid of?

Its spores resist destruction by heat

55

What can result in botulism poisoning?

Incomplete heating in the canning or bottling process

56

What is the botulism toxin?

A neurotoxin

57

What does the botulism toxin do?

Prevents the release of acetylcholine at the NMJ, thus preventing muscle contraction

58

How do patients with botulism present?

  • Descending flaccid paralysis
  • Dysphagia
  • Blurred vision
  • Eventual general paralysis

59

What does treatment of botulism involve?

  • Antitoxins,
  • Penicillin as the antibiotic
  • Ventilatory support

60

What do non-sporing anaerobes form?

The major part of the human bacterial flora of the mouth, intestine, vagina, and skin

61

What kind of infections are those by non-sproring anaerobes?

Endogenous

62

How do infections of non-sporing anaerobes occur?

Organisms escape from the normal flora into a new sterile anaerobic site

63

Give an example of how an infection of a non-sporing anaerobe could occur

Perforation of the large intestine

64

What happens once non-sporing anaerobes are established in their infective site?

They can multiply and cause tissue damage and spread

65

What are the main endogenous infections caused by non-sporing anaerobes?

  • Intra-abdominal abscesses
  • Liver abscesses
  • Lung abscesses
  • Dental abscess
  • Bone abscess
  • Leg ulceration

66

How do non-sporing anaerobes cause lung abscesses?

From aspiration pneumonia and subsequent formation of anaerobic compartment

67

What commonly happens with infection with non-sporing anaerobes?

They mix with aerobic bacteria and produce foul-smelling pus, which is quite characteristic

68

How is diagnosis of infection with non-sporing anaerobes made?

From spending specimens to the laboratory in anaerobic containers, and the cultures grown in selective media and under strict anaerobic conditions. The cultures can then be stained accordingly

69

What are the infections caused by non-sporing anaerobes mainly susceptible do?

Metronidazole

70

What are the main pathogens of anaerobic sepsis?

  • Bacteriodes fragilis
  • Prevotella melaninogenicus

71

Why is bacteriodes fragilis clinically relevant?

It is the most common of serious anaerobic infections

72

What is bacteriodes fragilis most commonly associated with?

Post-operative sepsis in abdominal or gynacological surgery

73

What feature does bacteriodes fragilis have?

Antiphagocytic capsule

74

What is the result of bacteroides fragilis' antiphagocytic capsule?

It inhibits phagocytosis of facultative organisms, promoting the development of synergistic infections

75

Where is Prevotella melaninogenicus common?

In dental abscesses and sinus infections