Anaerobic Pathogens

Question 1

clostridium sp.

Answer 1

*OBLIGATE ANAEROBIC
*gram POSITIVE rods
*FORM ENDOSPORES
*part of the normal flora

Question 2

clostridium difficile (C diff) - overview

Answer 2

*gram POS anaerobic rod that freely forms spores
*oxygen is toxic
*infection limited to large intestine
*disease is toxin-mediated (not invasive)

Question 3

clostridium difficile - virulence factors

Answer 3

1. Toxin A (enterotoxin) - causes cell death of intestinal mucosa
2. Toxin B (cytotoxin) - causes actin depolymerization

Question 4

C diff - toxin A (enterotoxin)

Answer 4

*chemotactic for neutrophils; stimulates infiltration of PMNs
*cytopathic effect: disruption of tight cell-to-cell junction
*increased permeability of intestinal wall and subsequent diarrhea

Question 5

C diff - Toxin B (cytotoxin)

Answer 5

*causes actin to depolymerize, with resultant destruction of cellular cytoskeleton

Question 6

3 required events to get C diff infection:

Answer 6

hospitalization (usually), followed by:
1) change in normal GI flora (ANTIBIOTICS)
2) acquire C diff spore (usually from environment or another person)
3) inadequate IgG response to toxins A and B

Question 7

what is the name of the disease caused by C diff infection

Answer 7

pseudomembranous colitis

Question 8

risk factors for C diff

Answer 8

**recent antibiotic exposure
*hospitalization
*recent GI surgery
*recent chemotherapy
*proton pump inhibitors

Question 9

what is the highly virulent strain of C diff in North America

Answer 9

BI/NAP1
*more likely to cause death

Question 10

C diff - clinical manifestation

Answer 10

*acute onset of severe, watery diarrhea
*fever, toxicity, high WBC count
**COMPLICATION = TOXIC MEGACOLON

Question 11

C diff - treatments

Answer 11

*oral vancomycin (recurrences can occur)
*stool transplant is highly effective for recurrent infections

Question 12

C diff - diagnosis

Answer 12

*demonstration of Toxin A and B in the stool by ELISA

Question 13

clostridium perfringens - overview

Answer 13

*gram positive rod
obligate anaerobe
**beta (DOUBLE RING) hemolysis

Question 14

what is the pathogen characterized by beta double ring hemolysis

Answer 14

clostridium perfringes

Question 15

clostridium perfringens - virulence factors

Answer 15

*alpha toxin - lyses erythrocytes and other cells; mediates massive hemolysis
*beta toxin - causes intestinal stasis and necrotic lesions
*enterotoxin - alters membrane permeability and causes diarrhea

Question 16

clostridium perfringens - clinical presentation (in soft tissues)

Answer 16

*GAS GANGRENE (characterized by gas formation)
*cellulitis, fasciitis, myositis with myonecrosis
*often follows trauma
*infection leads to muscle necrosis and septic shock
*can cause death within 24 hours

Question 17

clostridium perfringens - clinical presentation (food poisoning)

Answer 17

*only in intestine and only making enterotoxin
*causes watery diarrhea, abdominal cramps
*transmitted by poultry

Question 18

clostridium perfringens - diagnosis

Answer 18

*gram stain (gram + rods)
*anaerobic culture

Question 19

clostridium perfringens - treatment

Answer 19

high dose penicillin & surgical debridement

Question 20

clostridium tetani - overview

Answer 20

*anaerobic spore-forming
*gram positive rod
*classic “stepping on a rusty nail”

Question 21

clostridium tetani - virulence factors

Answer 21

*tetanus toxin (tetanospasmin)
*taken up by motor neurons (by pinocytosis)
*INHIBITS the INHIBITORY NEURON
*irreversible lack of inhibition of motor neuron produces tetanus (motor neuron is constantly active)

Question 22

primary host defense against clostridium tetani

Answer 22

antibodies against the tetanus toxin (this is why we get the vaccine)

Question 23

3 clinical entities of tetanus disease

Answer 23

1) generalized tetanus
2) localized tetanus
3) neonatal tetanus

Question 24

generalized tetanus

Answer 24

generalized musculature spasms involving the whole body

Question 25

localized tetanus

Answer 25

musculature spasms restricted to localized area of primary infection

Question 26

neonatal tetanus

Answer 26

neonatal infection primarily involving the umbilical stump; very high mortality
PREVENTION = vaccinate mom before delivery

Question 27

clostridium tetani - diagnosis

Answer 27

*clinical presentation (spasmatic paralysis)
*demonstration of seronegative state (no tetanus antibodies)

Question 28

clostridium tetani - treatment

Answer 28

*tetanus immunoglobulin (TIG) from CDC
*benzos (relax muscles)
*penicillin (decrease organism number - slowly)

Question 29

clostridium botulinum - virulence factor & its effect

Answer 29

*produces botulinum toxin - cleaves SNARE proteins so the Ach vesicle cannot attach to muscle to cause contraction
*causes FLACCID paralysis

Question 30

clostridium botulinum - primary host defense

Answer 30

antibody against the toxin (but we do not immunize against it)

Question 31

foodborne botulism

Answer 31

*initially - blurred vision, dry mouth, constipation, abdominal pain
*progression to bilateral descending weakness of peripheral muscles with flaccid paralysis

Question 32

other forms of clinical botulism

Answer 32

*infant botulism
*wound botulism
*inhalation botulism

Question 33

clostridium botulinum - diagnosis

Answer 33

*clinical presentation
*finding the suspected food source

Question 34

clostridium botulinum - treatment

Answer 34

*botulinum antitoxin (from CDC)

Question 35

anaerobic colonic gram NEGATIVE rods

Answer 35

*NON-spore forming
*LPS is a major virulence factor
*part of the normal flora
*obligate anaerobes
*there are a lot of these

Question 36

actinomyces sp.

Answer 36

*BRANCHING gram POSITIVE rods
*obligate anaerobes
*DENTATE appearing colonies on agar
*normal PERIODONTAL flora
*active infections tend to produce and “SPIT OUT” “SULFUR GRANULES” in pus
*tend to cross tissue planes