Clostridium botulinum and Clostridium difficile

Question 1

General features and habitat of Clostridium Botulinum

Answer 1

Gram +
Rod shape
Reservoir- soil and dust

Question 2

Biochemical Properties of Clostridium Botulinum

Answer 2

Obligate anaerobe (to distinguish from Bacillus species) 
Spore forming

Question 3

Pathogenesis of Clostridium Botulinum

Answer 3

Transmitted by eating improper canned food and honey (where spores can survive) Can also be transmitted by infected wound (i.e. trauma)

The botulinum toxin is a AB type neurotoxin (heat labile- 10 mins at 60C inactivate it).

1. Toxins from germinated spores are absorbed by the gut and then carried by blood to
the PNS (can’t cross BBB into CNS)

2. In the PNS, it acts as a protease and cleaves the SNARE protein, inhibiting the release
   of Acetylcholine from motor neurons, resulting in a reversible flaccid paralysis

Question 4

Clinical Features (Botulism) of Clostridium Botulinum

Answer 4

Adults botulism: foodborne intoxication due to pre-formed toxins (already found in untreated canned food)

Flaccid paralysis (unlike tetanus)
Descending paralysis- eye symptoms occur first then goes down

Ptosis (eyelid dropping) and diplopia (double vision)

Abdominal pains

Respiratory arrest (paralysis of diaphragm) and death

Infantile botulism “floppy baby syndrome”: infection caused by toxin produced in vivo (in the gut) due to ingestion of spores (found in honey)

Flaccid paralysis, diplopia, dysphagia, constipation, weak feeding and crying. May lead to respiratory arrest

Question 5

Diagnosis of Clostridium Botulinum

Answer 5

Isolation of bacteria or toxin from feces, food or serum (latter- in case of toxin)

Toxin detection- mouse inoculation, usually with patient’s serum

Serology- ELISA

Question 6

Treatment of Clostridium Botulinum

Answer 6

Passive immunization- polyvalent (serotypes A-G)

antitoxin serum

Question 7

General Features of Clostridium difficile

Answer 7

Gram +
Rod shape

Reservoir- human intestinal flora (in newborns ~70%, in adults ~1-2%)

Question 8

Biochemical Properties of Clostridium difficile

Answer 8

Obligate anaerobe (to distinguish from Bacillus species) 
Spore forming

Question 9

Pathogenesis of Clostridium difficile

Answer 9

Nosocomial infection- e.g. improper washing of hands by healthcare providers.
Spores can also spread easily from patient to patient and relapse in (spores still remain) Usually, cannot compete with normal gut flora but increased risk in patients taking antibiotics (e.g. Clindamycin)

A toxin (enterotoxin)
Binds to brush border of intestine and damage it enzymes, leading to inflammation, cell death (hemorrhagic necrosis) and increasing of fluid secretion (i.e. diarrhea)

B toxin (cytotoxin)
Disrupts cytoskeleton integrity by depolymerizing actin- causing enterocyte necrosis This leads to a build-up of yellowish-gray exudate forming pseudomembrane covering the colon mucosa

Binary toxin (serotype 027)- ADP rybosilation toxin; highly virulent strain (severe cases)

Question 10

Clinical Features of Clostridium difficile

Answer 10

Watery diarrhea- by A toxin (also known as “Antibiotic Associated Diarrhea”- AAD):
Severe watery diarrhea and colitis (inflammation of colon)

Pseudomembrane colitis- by B toxin: Pseudomembranes on colon mucosa with colitis

Question 11

Diagnosis of Clostridium difficile

Answer 11

Rapid assay- toxins detection in stool (and not bacteria itself) by ELISA, PCR or IC

Culture on CCFA medium (Cycloserine-Cefoxitin Fructose Agar)- selective for C. difficile Colonies are flat, irregular margins, gray in color and with “barnyard” odor

Question 12

Treatment of Clostridium difficile

Answer 12

Stop the original antibiotic treatment (e.g. Clindamycin)
Oral Vancomycin
Metronidazole
Fecal transplantation may also be used

Question 13

Prevention of Clostridium difficile

Answer 13

Thoroughly hand cleaning, separation of patients