Gram-positive — Flashcards

Flashcard 31: What is the mechanism of action of Exotoxin A (SpeA) in S. pyogenes?

Answer: Superantigen; cross-links MHC II and T-cell receptor (VB region), leading to overwhelming release of IFN-γ and IL-2.

Extra: Causes Streptococcal Toxic Shock-like Syndrome (STSS). Presents with fever, rash, and shock. Note: Compare with Pseudomonas Exotoxin A, which inhibits EF-2 via ADP-ribosylation.

Flashcard 32: toxic shock syndrome toxin (TSST-1)

Answer: Staphylococcus aureus

Extra: superantigenMHCII stimulation, overwhelming release of IFN-γ and IL-2rash, fever, shock (i.e. toxic shock)

Flashcard 33: streptolysin O

Answer: Streptococcus pyogenes

Extra: lyses cell membranesdegrades cell membranesβ-hemolysis

Flashcard 34: alpha toxin

Answer: Clostridium perfringens

Extra: lyses cell membranesphospholipase degrades cell membranes and tissuesmyonecrosis and hemolysis

Flashcard 35: Diphtheria toxin

Answer: Corynebacterium diphtheriae

Extra: Protein synthesis inhibitor; inactivates elongation factor 2 (EF-2). Clinical features: pseudomembranous pharyngitis, severe lymphadenopathy (bull neck appearance).

Flashcard 36: Give some diseases caused by exotoxins.

Answer: tetanus, botulism, diptheria

Flashcard 37: Give examples G+ filamentous bacteria.

Answer: Actinomyces, Nocardia

Flashcard 38: Give examples of G+ bacilli.

Answer: Clostridium, Corynebacterium, Bacillus, Listeria, Gardnerella, Mycobacterium (only stained by acid fast, but structurally G+)

Flashcard 39: Give examples of G+ cocci.

Answer: Staphylococcus, Streptococcus

Flashcard 40: Which cellular structures are unique to G+ bacteria?

Answer: cell wall, lipoteichoic acid