Gram + Rods/Bacilli

Question 1

Clostridium difficile

strict anaerobe, spore formation

Answer 1

Common cause of nocosomial diarrhea (spores not killed by alcohol/arise when treating other infections with Clindamycin) -
Exotoxin A –> targets GI brush border (diarrhea) -
Exotoxin B –> binds to cytoskeleton of enterocytes –> pseudomembrane formation
Dx by toxin assay; Tx oral vancomycin, metronidazole

Question 2

Clostridium tetani

strict anaerobe, spore formation

Answer 2

Common in soil and GI tract - spores germinate, bacteria produces tetanus toxin - retrograde axonal transport –> blocks inhibitory interneurons by interfering with vessicular transport (Cleaves SNARE protein, decreasing GABA and Glycine secretion from Renshaw cells)
Causes spastic paralysis (lock jaw, opisthotonus)
Tx with toxoid vaccine to prevent further neural destruction

Question 3

Clostridium botulinum

strict anaerobe, spore formation

Answer 3

Common in soil and GI tract - commonly seen in families that consume improperly canned food (where spores germinate and produce toxin)
Botulinum toxin is absorbed in the gut and travels to motor neurons –> cleaves SNARE protein to inhibit Acetycholine release
Causes flaccid paralysis - “floppy baby” when consumes spores from honey

Question 4

Clostridium perfringens

strict anaerobe, spore formation

Answer 4

Spores in soil
Wound Infection - cause GAS gangrene, myonecrosis by a-toxins, lethincinase cleaves phospholipids (creates double-zone of hemolysis on plates)
Food poisoning - late onset due to large intake of bacteria/spores –> enterotoxin formation –> disrupts tight junctions of ileum epithelium
Tx- IV penicillin G for wounds, oral antibiotics for food poisoning