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Immunology Pt. 2 > Anaerobic Bacteria > Flashcards

Anaerobic Bacteria Flashcards

1
Q

Infections by anaerobes are ______, _______ infections

A

mixed, opportunistic

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2
Q

What types of surfaces contain hundreds of species of anaerobes

A

mucosal surfaces

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3
Q

Why are anaerobes sensitive to O2 intermediates?

A

Have little superoxide dismutase to remove O2 radicals
Have low amounts of catalase to remove H2O
Often lack cytochromes

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4
Q

How do aerobic and anaerobic bacteria work together

A

The aerobic bacteria metabolize O2, making the environment favorable for anaerobes

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5
Q

Anaerobic gram negative pathogens: site of infections

A

Colon, mouth, and skin

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6
Q

Anaerobic infections are often _____ ______ due to short fatty acids produced during fermentations

A

foul smelling

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7
Q

What is a general product of fermentations

A

gas

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8
Q

Polymicrobial nature of anaerobic infection

A

Infections often due to the contamination of tissue by normal flora

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9
Q

Bacteriodes fragilis

A

most intra-abdominal infections

Common inhabitant of bowel

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10
Q

Bacteriodes Fragilis: virulence factor

A
  • Polysaccharide capsule
  • Bacteroides are aerotolerant anaerobes able to tolerate atmospheric concentrations of oxygen
  • Bacteroides encode two major oxidative stress response genes, catalase and superoxide dismutase
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11
Q

B. Fragilis often in mixed infection with:

A
  • Other anaerobes

- Facultative anaerobes (Peptostreptococcus)

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12
Q

Clostridia

A

Anaerobic Gram Positive, spore forming bacilli; obligate anerobes are aerotolerant

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13
Q

Clostridia
Pathogensis:
Physiology:

A

Pathogenesis: usually due to an exotoxin
Physiology: either - saccharolytic - sugars
- proteolytic - amino acids

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14
Q

Clostridia groups

A

Gastrointestinal disease: C. difficile
Histotoxic clostridia: C. perfringens
Tetanus: C. tetani
Botulism, food poisoning: C. botulinum

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15
Q

Clostiridia are ____ inhabitants or inhabitants of the ______ _____

A

Soil; Intestinal tract

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16
Q

Antibiotic-associated diarrhea

A

C. difficile (Toxins A and B)
- antibiotic therapies are associated with C. difficile infections where the normal flora are reduced allowing endogenous and ingested C. difficile to expand and produce Toxin A and Toxin B which contribute to diarrhea and inflammation

17
Q

C. difficile pathology

A

Toxin A and Toxin B glucosylate Rho GTPases which causes actin depolymerization → disrupt gut epithelial cells
UDP-glucose + Rho → Rho-glucose (inactive) + UDP

18
Q

C. dificile treatment

A

Metronidazole, vancomycin, or a subset of fluoroquinolines

19
Q

Histotoxic clostridia

A

Invasive; C. perfringens - cause majority of clostridial-mediated myonecrosis

20
Q

C. perfringens pathology:

A

A deep wound to muscle predisposes infection

  • Reduction of tissue redox potential (host cell death)
  • Host proteases: release nutrients (Clostridia grow)
  • C. perfringens → alpha toxin (phospholipase) - gas gangrene
21
Q

Clostridial neurotoxins

A

C. tetani (spastic paralysis), C. botulinum (flaccid paralysis)

22
Q

Neurotoxins

A

150 kDa single protein with an A:B structure-function organization 7 serotypes of Botulinum toxin (BoNT) A,B,C,D,E,F and G defined antisera neutralization and tetanus toxin

23
Q

Clostridium neurotoxins cleave _____ proteins and inhibit ______ _____ ______

A

SNARE; synaptic vesicle fusion

24
Q

BoNT inhibits release of ___________ at presynaptic membrane of peripheral neurons; yields ____ ______

A

acetylcholine; flaccid paralysis

25
Q

TeNT is transported in the __________ to inhibit interneuron function; yields _______ ______

A

CNS; spastic paralysis

26
Q

Tetanus - C. tetani
Physiology:
Pathogenicity:

A

Physiology: anaerobe, proteolytic - peptide and amino acid
Pathogenicity: C. tetani is not invasive - remains at site of infection
- Following injury with a mixed infection (soil)
- Other bacteria ferment to reduce redox potential
- Allows limited growth of C. tetani, but sufficient for toxin production

27
Q

Why do botulinum toxin and tetanus toxin elicit unique pathologies

A

BoNT enters through vescile and affects presynaptic neuron

TeNT has endosomal entry and follows retrograde trafficking to inhibit interneuron function

28
Q

Treatment of tetanus toxin

A

Tetanus toxin → Tetanus toxoid (preventative)
Vaccinate Td or Tdap - stimulate an antibody response to toxin
Administer antibiotics
Administer anti-TT antibody (neutralize circulating toxin)

29
Q

How are botulinum toxin serotypes defined?

A

Absence of cross neutralization by antisera

30
Q

Most toxic protein toxins for humans

A

Botulinum toxin and Tetanus toxin

31
Q

Which botulism serotypes are most common in humans

A

A, B and E

32
Q

Three natural intoxications and infections associated with BoNT

A
  1. Food-borne (intoxicaton - toxin produced from food)
  2. Infant botulism (spores ingested)
  3. Wound botulism ( spores in wound)
33
Q

Botulinum toxin implicated as agent of _____ ______

A

biological warfare

34
Q

Are botulism and botulinum toxin contagious?

A

no

35
Q

Treatment of botulinum toxin

A
  • No licensed vaccine
  • Supportive care
  • Passive immunization and antitoxin
  • CDC has anti- A,B, E sera: US army anti A-G sera
36
Q

Why are BoNTs clinically useful

A

BoNTs have dual neuron specificity

  • BoNTs bind specifically to receptors on neurons
  • Cleave neuronal SNARE substrates
  • High specifcity and potency for targeted neurons
37
Q

Blepharospasm

A

Abnormal contraction or twitch of eyelid neurons (functional blindness)

38
Q

Serotypes for Botox and Myoboc

A

Botox: Serotype A
Myoboc: Serotype B

Immunology Pt. 2 (11 decks)

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