20 Anaerobes 1 (Clostridium)

Question 1

T/F

After a stay of two days in a hospital, 10% of patients will develop infection with C. difficile

Answer 1

True

Question 2

What are general characteristics of anaerobes?

Answer 2

• grow better in anaerobic atmosphere
• lack mechanisms of oxygen metabolism and/or detoxification
• should be considered when signs of infection but aerobic culture negative

Question 3

What are general characteristics of anaerobe infections?

Answer 3

• Adjacent to surfaces that normally harbor anaerobes as normal flora (e.g. mucosal surface)
• Abscess formation or tissue necrosis
• Putrid odor (fermentation)
• Gas formation
• Polymicrobic infection or organisms that look like anaerobes

Question 4

What level of blood supply promotes anaerobic growth?

Answer 4

Poor blood supply > low O2 levels

Question 5

Basic lab characteristics of genus Clostridium?

Answer 5

anaerobic G+ rods

spore formers

Question 6

Which Clostridium species is non-motile, is a large rectangular rod, and rarely forms spores?

Answer 6

Clostridium perfringens

Question 7

Which bacterium produces this group of exotoxins?
alpha toxin (lecithinase)
beta toxin
epsilon toxin
iota toxin
heat-labile enterotoxin
collagenase

Answer 7

Clostridium perfringens

Question 8

What characteristic divides Clostridium perfringens into 5 types?

Answer 8

exotoxins

Question 9

How does each exotoxin secreted by Clostridium perfringens contribute to disease?
alpha toxin (lecithinase)
beta toxin
epsilon toxin
iota toxin
heat-labile enterotoxin
collagenase

Answer 9

Alpha toxin (lecithinase) - massive hemolysis, increased vascular permeability, tissue destruction, hepatic toxicity, myocardial dysfuntion
Beta toxin - intestinal stasis, necrotizing enteritis
Epsilon toxin - increased vascular permeability of GI wall
Iota toxin - increased vascular permeability, necrosis
Collagenase - penetration deep into tissues -> fulminating gangrene
Heat-labile enterotoxin - no other info

Question 10

Where is Clostridium perfringens found in the environment? Is it part of the human microbiome?

Answer 10

Spores are in soil and water
Found in the intestinal tract of animals
Yes, found in the intestinal and genito-urinary tracts of humans

Question 11

What is the cause of Clostridial food poisoning? What form is it ingested in? Symptoms?

Answer 11

Clostridium perfringens
Ingestion of preformed toxin, which inserts in membrane of SI altering permeability -> diarrhea
Watery diarrhea and crampy abdominal pain 8-24 hours post ingestion

Question 12

What infections/diseases are caused by Clostridium perfringens?

Answer 12

Cellulitis
Fasciculitis/suppurative myositis
Myonecrosis
Anaerobic puerperal sepsis
Septic abortions
Clostridial food poisoning
Necrotizing enterocolitis

Question 13

What is the mode of infection, complications, and death from Clostridium perfringens soft tissue infections?

Answer 13

• spores germinate and vegetative cells grow in traumatized tissue; degradative enzymes ferment carbohydrates and produce gas in tissue
• bacteria produce necrotizing toxin and hyaluronidase; tissue necrosis extends resulting in incr. bacterial growth, hemolytic anemia, severe toxemia, renal failure, and death

Question 14

How is a C. perfringens infection diagnosed?

Answer 14

appearance and foul smell, smears showing large G+ rods, spores not usually seen, double zone of hemolysis on blood agar

Question 15

Which exotoxin is most responsible for causing necrotizing enterocolitis?

Answer 15

beta toxin

Question 16

What infection(s)/disease(s) are caused by C. difficile?
Symptoms?

Answer 16

• pseudomembraneous colitis

- range from non-bloody diarrhea to severe life-threatening pseudomembranous colitis with fever and abdominal cramping

Question 17

Which bacterium produces this group of exotoxins?
enterotoxin (toxin A)
cytotoxin (toxin B)

Answer 17

C. difficile

Question 18

How does each exotoxin secreted by Clostridium difficile contribute to disease?

Answer 18

Enterotoxin (toxin A) - stimulates infiltration of PMNs into the ileum -> inflammation
Cytotoxin (toxin B) - glycosylates G proteins involved in actin filament polymerization & depolymerization -> loss of cytoskeletal integrity -> death of enterocytes & inflammation

Question 19

What is the cause of increased virulence of the hypervirulent strain of C. difficile?

Answer 19

produces increased levels of toxins A & B

Question 20

How is a C. difficile infection diagnosed?

Answer 20

Isolation from feces and testing for toxins

Question 21

How is pseudomembranous colitis treated?

Answer 21

Metronidazole

may require surgical repair of intestines and stool transplant

Question 22

Which Clostridium species is non-motile, is a large rectangular rod, and produces round terminal spores (drumstick/tennis racket bacilli)?

Answer 22

Clostridium tetani

Question 23

What toxin(s) does C. tetani secrete?
What disease symptoms result?

Answer 23

Tetanospasmin (tetanus toxin) - plasmid-encoded heat labile A-B neurotoxin; acts by cleaving neurotransmitter inhibitors resulting in spastic paralysis and muscle spasms

Question 24

What is the mode of infection for neonatal sepsis?

Answer 24

Spores enter via contaminated umbilicus/circumcision

Question 25

What is the clinical significance of a C. tetani infection?

Incubation period? Mortality rate?

Answer 25

Incubation period 3-21 days (variable)

Death results from compromised breathing (50% mortality)

Question 26

How is a C. tetani infection diagnosed?

Answer 26

In most cases diagnosed based on signs, symptoms, and patient history
organism rarely cultured from wounds and antibodies/tetanus toxin are not detected in patients

Question 27

How many doses of vaccine must a patient have received so that no tetanus prophylaxis is not necessary?
What is this prophylaxis

Answer 27

3 or more
Clean minor wounds give tetanus toxoid and metronidazole
All other wounds give tetanus toxoid and tetanus immune globulin

Question 28

What bacterium produces the most lethal toxin known?

Answer 28

C. botulinum

botulinum neurotoxin

Question 29

What is the incubation period and symptoms of botulinum toxin ingestion?

Answer 29

12-36 hours after ingestion begins with nausea, vomiting, and bilateral CN impairment
then drooping eyelids, double/blurred vision, difficulty articulating words & swallowing
then paralysis descends to involve muscles of thorax and extremities leading to death from respiratory and cardiac failure

Question 30

What is the pathogenesis/mode of action of the botulinum neurotoxin?

Answer 30

Synthesized during growth as zinc-endopeptidase (an A-B toxin)
Inactivates proteins regulating ACh release from nerve termini, blocking neurotransmission at synapses and resulting in flaccid paralysis

Question 31

What is necessary for recovery after the effects of the botulinum neurotoxin?

Answer 31

regeneration of nerve endings (takes months to years)

Question 32

What is the treatment of botulinum neurotoxin ingestion?

Answer 32

ventilator support, gastric lavage, metronidazole, and injection of trivalent (A, B, E) botulinum antitoxin

Question 33

How it botulism foodborne intoxication diagnosed?

Answer 33

based on symptoms and past history (organism not usually cultured)
confirm diagnosis with mouse protection test

Question 34

What is infant botulism? Age affected? Mode of infection? Signs/symptoms?

Answer 34

infected infants 3 weeks-6 months old
preformed toxin not detected in any food - bacterial spores ingested (honey, infant milk powder) and germinate colonizing in intestinal tract
constipation, lethargy with feeding difficulties; followed by marked loss of muscle tone, especially in the head and neck

Question 35

What are the 3 forms of botulism infection/toxin ingestion?

Answer 35

Foodborne intoxication
Infant botulism
Wound botulism

Question 36

What is the cosmetic use of a Clostridium species?

Answer 36

C. botulinum toxin A used cosmetically (Botox) to remove wrinkles or as muscle relaxant

Question 37

T/F

Botulinum vaccine exists

Answer 37

True but immunization of general population not warranted since disease so rare

Question 38

What other Clostridium species is associated with infections in IUDs and cancer patients?

Answer 38

C. novyi