Anaerobic Bacteria

Question 1

Infections by anaerobes are ______, _______ infections

Answer 1

mixed, opportunistic

Question 2

What types of surfaces contain hundreds of species of anaerobes

Answer 2

mucosal surfaces

Question 3

Why are anaerobes sensitive to O2 intermediates?

Answer 3

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

Question 4

How do aerobic and anaerobic bacteria work together

Answer 4

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

Question 5

Anaerobic gram negative pathogens: site of infections

Answer 5

Colon, mouth, and skin

Question 6

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

Answer 6

foul smelling

Question 7

What is a general product of fermentations

Answer 7

gas

Question 8

Polymicrobial nature of anaerobic infection

Answer 8

Infections often due to the contamination of tissue by normal flora

Question 9

Bacteriodes fragilis

Answer 9

most intra-abdominal infections

Common inhabitant of bowel

Question 10

Bacteriodes Fragilis: virulence factor

Answer 10

• 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

Question 11

B. Fragilis often in mixed infection with:

Answer 11

• Other anaerobes

- Facultative anaerobes (Peptostreptococcus)

Question 12

Clostridia

Answer 12

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

Question 13

Clostridia
Pathogensis:
Physiology:

Answer 13

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

Question 14

Clostridia groups

Answer 14

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

Question 15

Clostiridia are ____ inhabitants or inhabitants of the ______ _____

Answer 15

Soil; Intestinal tract

Question 16

Antibiotic-associated diarrhea

Answer 16

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

Question 17

C. difficile pathology

Answer 17

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

Question 18

C. dificile treatment

Answer 18

Metronidazole, vancomycin, or a subset of fluoroquinolines

Question 19

Histotoxic clostridia

Answer 19

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

Question 20

C. perfringens pathology:

Answer 20

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

Question 21

Clostridial neurotoxins

Answer 21

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

Question 22

Neurotoxins

Answer 22

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

Question 23

Clostridium neurotoxins cleave _____ proteins and inhibit ______ _____ ______

Answer 23

SNARE; synaptic vesicle fusion

Question 24

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

Answer 24

acetylcholine; flaccid paralysis

Question 25

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

Answer 25

CNS; spastic paralysis

Question 26

Tetanus - C. tetani Physiology: Pathogenicity:

Answer 26

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

Question 27

Why do botulinum toxin and tetanus toxin elicit unique pathologies

Answer 27

BoNT enters through vescile and affects presynaptic neuron | TeNT has endosomal entry and follows retrograde trafficking to inhibit interneuron function

Question 28

Treatment of tetanus toxin

Answer 28

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

Question 29

How are botulinum toxin serotypes defined?

Answer 29

Absence of cross neutralization by antisera

Question 30

Most toxic protein toxins for humans

Answer 30

Botulinum toxin and Tetanus toxin

Question 31

Which botulism serotypes are most common in humans

Answer 31

A, B and E

Question 32

Three natural intoxications and infections associated with BoNT

Answer 32

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

Question 33

Botulinum toxin implicated as agent of _____ ______

Answer 33

biological warfare

Question 34

Are botulism and botulinum toxin contagious?

Answer 34

no

Question 35

Treatment of botulinum toxin

Answer 35

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

Question 36

Why are BoNTs clinically useful

Answer 36

BoNTs have dual neuron specificity - BoNTs bind specifically to receptors on neurons - Cleave neuronal SNARE substrates - High specifcity and potency for targeted neurons

Question 37

Blepharospasm

Answer 37

Abnormal contraction or twitch of eyelid neurons (functional blindness)

Question 38

Serotypes for Botox and Myoboc

Answer 38

Botox: Serotype A Myoboc: Serotype B