SPORE FORMING Bacilli- Anaerobic- Clostridia (Lecture 16)

C. tetani, C. botulinum, C. Perfringens, C. difficile

What are the structural features of SPORE FORMING Bacilli- Anaerobic- Clostridia?

Gram Positive (some are gram negative)

Anaerobic

ENDOSPORE forming

Rod shaped

What are the clinical manifestations of SPORE FORMING Bacilli- Anaerobic- Clostridia?

Cause MONOMICROBIAL exogenous infections

What are the structural features of Clostridium tetani?

Large

motile rod shaped

Produces terminal spores

TETANOSPASMIN

• plasma-encoded

• heat-labile neurotoxin

What is TETANOSPASMIN?

Neurotoxin produced by C. tetani

A-B toxin that inactivates proteins that regulate the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA)

What are the clinical manifestations of C. tetani?

Generalized tetanus

• generalized musculature spasms and ANS involvement in severe disease

• lock jaw most common form

Localized tetanus

• Musculature spasms restricted to a localized area

• Cephalic tetanus is a variation

Neonatal tetanus

• Involves infection of umbilical stump

• High mortality

What are the treatments of C. tetani?

Debridement of primary wound.

Penicillin or metronidazole

Passive immunization with antitoxin globulin, tetanus toxoid

Three doses of tetanus toxoid vaccine followed by booster every 10 years

What are the structural features of C. botulinum?

Large

Spore-forming rods

Ubiquitous spores in soil worldwide

BOTULINUM TOXIN

What is BOTULINUM toxin?

Heat-labile neurotoxin complexed with nontoxic proteins for protection through the digestive tract.

A-B toxin inactivates proteins that regulate the release of ACH.

HUMAN disease is associated with types A, B, E, and F

What are the clinical manifestations of C. botulinum?

Deadliest Poison on EARTH— Less than 1 microgram is fatal for a human

Foodborne botulism can cause BLURRED VISION

Infant, wound, and inhalation botulism has a HIGH MORTALITY rate

What is the treatment for C. botulinum?

Combination of Metronidazole or Penicillin

Trivalent botulinum antitoxin and ventilatory support.

What are the structural features of C. perfringens?

Large

Rectangular gram POSITIVE rods

Grows in digestive tract of animals and humans

Rarely forms ENDOSPORES in vivo or in vitro

ENTEROTOXIN

What is ENTEROTOXIN?

From C. perfringens

Binds to receptors on brush border membrane of the small intestine epithelium in the ileum and jejunum.

Acts as SUPERANTIGEN

What are the clinical manifestations of C. perfringens?

Type A toxin types strains are responsible for most human infections

Soft tissue infections

Cellulitis

Enteral infections— food poisoning, no fever, nausea, or vomiting.

Necrotizing enteritis

What is the treatment for C. perfringens?

Symptomatic treatment for food poisoning

Sever infections require surgical debridement

HIGH DOSE penicillin therapy.

What are the structural features of C. difficile?

ENTEROTOXIN (Toxin A)

• Stimulates neutrophil infiltration into ilium and cytokine release

CYTOTOXIN (toxin B)

• Damages intestinal epithelial cell cytoskeleton by causing actin filaments to depolymerize.

Tag team to make the disease

What are the clinical manifestations of C. difficile?

Most common clostridial pathogen responsible for antibiotic-associated gastrointestinal diseases.

Antibiotic-associated diarrhea

Pseudomembranous colitis-most SEVERE form of C. difficile

What is the treatment for C. difficile?

Discontinue implicated antibiotic switch to fidaxomicin or vancomycin

Relapse is common because antibiotics do not kill spores

Fecal transplantation