Gram Positive Rods

Question 1

What distinctive feature does bacillus anthracis have in its capsule?

Answer 1

Is made by polypeptide [polyD-glutamate] (no peptidoglycan as almost all gram positive)

Question 2

Major virulence factor of bacillus anthracis

Answer 2

Anthrax toxin: 3 components

• protective antigen (B component)
• lethal factor
• edema factor

Question 3

Toxins of bacillus cereus. Disease associated.

Answer 3

Emetic toxin (1-6 hours to act) - fried rice associated
Diarrheal toxin (18 hours to act) - ⬆️ cAMP ▶️ watery diarrhea 
Rapid-onset gastroenteritis

Question 4

Mechanism of action of tetanus toxin.

Answer 4

Carried intra-axonally to CNS ▶️ binds to ganglioside receptors ▶️ block release on GABA and glycine at spinal synapses ▶️ extreme muscle spams (unopposed excitatory signal sustained)

Question 5

How do you treat intoxication and infection by clostridium botulinum?

Answer 5

Infection (child) ▶️ hyperimmune human serum
Intoxication (adult) ▶️ trivalent (ABE) antitoxin
Supportive care, respiratory support in ICU monitored

NO ANTIBIOTICS ▶️ may worsen or prolong

Question 6

Which are the toxins and disease associated of clostridium perfringes?

Answer 6

Alpha toxin (phospholipase C) ▶️ lecithinase ▶️ massive hemolysis and myonecrosis ▶️ gas gangrene
Enterotoxin ▶️ disrupt ion transport ▶️ watery diarrhea

Question 7

How is coded the botulinum toxin?

Answer 7

Prophage (lysogenized clostridium botulinum)

Question 8

Toxins of clostridium difficile. Mechanism of disease.

Answer 8

Toxin A ▶️ Enterotoxin damage mucosa ▶️ fluid ⬆️, attract granulocyte
Toxin B ▶️ cytotoxin, cytopathic

Question 9

Toxins of listeria monocytogenes. Mechanism of disease.

Answer 9

Listeriolysin O (a B-hemolysin) ▶️ rapid scape from phagosome to cytoplasm before lysosome fuses

Question 10

Risk for the baby if during pregnancy the mother eat “deli food”. Why? Cause of it.

Answer 10

Granulomatosis infantisepticum

Listeria monocytogenes can cross the placenta

Question 11

What do you use to diagnose Diphteria?

Answer 11

Elek test ▶️ identifies toxin production

*ELISA for toxin is the frontline

Question 12

Toxin of corynebacterium diphteriae. Mechanism of disease.

Answer 12

Diphteria toxin (A-B component) ▶️ add ADP-ribose to eEF-2 ([-] enlongation) ▶️ (-) protein synthesis

Question 13

How is the general presentation and progress of the actinomycosis?

Answer 13

Tissue swelling ▶️ draining abscesses (sinus tracts) ▶️ “sulfur” granules (hard yellow colonies) in exudate ▶️ used in microscope or culture to dx.

Question 14

Classic presentation of actinomycosis in face and CNS? How can both occur?

Answer 14

• face: “lumpy jaw” ▶️ dental trauma or poor oral hygiene
• CNS: solitary brain abscess (different with nocardia - multiple foci)

*also can present in pelvis, abdomen, trorax.

Question 15

What important and prevalent disease recalls pulmonary nocardiosis, what do they have in common and how can differentiate them?

Answer 15

Nocardiosis vs Tuberculosis

Cavitary (common point) bronchopulmonary Nocardiosis ▶️ partial acid fast or branching rods (differentiate with TB)

Question 16

Nocardiosis, diseases, spread of them, and treatment.

Answer 16

• cavitary bronchopulmonary Nocardiosis (N. asteroides) ▶️ spread to CNS (multifoci brain abscesses)
• cutaneous/subcutaneous Nocardiosis (N. brasiliensis) ▶️ mycetoma (no “sulfur” granules - differentiate of actinomycosis)

Question 17

How does mycobacterium tuberculosis avoid intracellular killing by macrophages? What other virulence factor does it use?

Answer 17

Sulfatides (sulfolipids) ▶️ (-) phagosome-lysosome fusion
*if fusion occurs waxy cell wall reduces killing effect
Cord factor ▶️ blocks mitochondrial respiration (oxidative phosphorylation), (-) leukocyte migration

Question 18

Gram (+) rode that grow at 4 grades C

Answer 18

Listeria monocytogenes