Clostridium tetani
What type of organism is Clostridium tetani?
Gram-positive, obligate anaerobic, spore-forming, motile bacillus with terminal spores (drumstick appearance).
How is S. aureus identified in the lab?
Gram-positive cocci in clusters, catalase positive, coagulase positive, mannitol fermentation positive.
What hemolysis pattern does it show?
Beta-hemolysis (complete hemolysis).
What type of organism is it?
Gram-negative, aerobic, oxidase-positive rod.
What type of organism is it?
Gram-positive, anaerobic, spore-forming, non-motile bacillus.
What is the name of its toxin and what type is it?
Tetanospasmin; an A-B exotoxin encoded on a plasmid.
What toxin causes toxic shock syndrome?
TSST-1 (superantigen → massive cytokine release).
Is it catalase positive or negative?
Catalase negative
What pigment does it produce?
Pyocyanin (blue-green).
What is the main toxin?
Alpha toxin (lecithinase, phospholipase C).
What is the exact mechanism of tetanospasmin?
It blocks release of inhibitory neurotransmitters (GABA and glycine) from interneurons in the spinal cord by cleaving synaptobrevin → prevents vesicle release.
Why does S. aureus food poisoning have rapid onset?
Because it is caused by ingestion of preformed enterotoxin (not infection).
What is the most important virulence factor?
M protein (anti-phagocytic)
Which patients are most at risk?
Burn patients, cystic fibrosis, immunocompromised, hospitalized patients.
What disease does it cause in deep wounds?
Gas gangrene (clostridial myonecrosis).
What are the classic clinical signs?
Trismus (lockjaw), risus sardonicus, opisthotonus, muscle spasms, autonomic instability.
Which valve is most commonly affected in IV drug users?
Tricuspid valve
What causes rheumatic fever?
Molecular mimicry between M protein and cardiac tissue → autoimmune reaction.
Why is it difficult to treat?
Intrinsic multidrug resistance + biofilm formation.
Why does gas form in tissues?
Fermentation of carbohydrates under anaerobic conditions → gas production.
What is the complete treatment protocol?
Human tetanus immune globulin (neutralizes toxin)
Metronidazole
Wound debridement
Benzodiazepines for muscle spasm
Vaccination update
First-line treatment for MRSA
Vancomycin
Treatment of choice?
Penicillin
Name 2 effective antibiotics.
Piperacillin-tazobactam, ceftazidime, carbapenems, aminoglycosides.
Emergency management?
Immediate surgical debridement + high-dose penicillin + hyperbaric oxygen.