General Microbiology

Question 1

What microorganism of oral normal flora can cause endocarditis? Why does it occur?

Answer 1

Streptococcus viridans

Misplaced

Question 2

What mechanism generally do the viruses use to cause cell damage?

Answer 2

• Main: intracellular replication ▶️ kills cells

- may no noticeable damage ▶️ latent viruses

Question 3

What bacteria can use invasins?

Answer 3

Yersinia pseudotuberculosis

Question 4

Specific pathogenic part of LPS, what type of toxin is it? Which organisms have them?

Answer 4

Lipid A portion
Endotoxin
Gram (-)

Question 5

Principal mechanism of pathogenicity of the Endotoxin

Answer 5

(+) macrophages ▶️ IL-6, IL-1, TNF-alfa ▶️ tissue damage
Bradykinin-induced vasodilation ▶️ endothelial damage ▶️ shock
(+) Hageman factor ▶️ coagulation (DIC)

Question 6

Type of toxins that can be used to produced as vaccine by modification with chemicals and heat. What components do they have? Functions of them.

Answer 6

Exotoxin
B component: binding to cell receptor, facilitate internalization of A
A component: active, ADP ribosyl transferase

Question 7

What do the cytolysins do? Examples.

Answer 7

Lyse cells from outside by membrane damage

• lecithinase ▶️ C. perfringes (gangrene, myonecrosis)
• Alfa toxin ▶️ staphylococcus aureus ▶️ pores in membrane

Question 8

Which exotoxins interferes with 60S ribosomal subunit? Clinical and molecular result.

Answer 8

• shiga toxin ▶️ shigella dysenteriae
• Verotoxin ▶️ enterohemorrhagic E. coli (EHEC)
• (-) protein synthesis in eukaryotic cells ▶️ bloody diarrhea

Question 9

Superantigen of staphylococcus aureus, actions of it.

Answer 9

TSST-1 ▶️ ⬆️ susceptibility to LPS (endotoxin), shock, capillary leakage

Question 10

Clue to suspect about a microorganism that is a fungus?

Answer 10

Complex carbohydrate cell wall (chitin, glucan, manan)

*remember the can be referred as gram (+) because its thick wall retains gram stain

Question 11

What do the enterotoxigenic E. coli toxin (Heat labile toxin) and cholera toxin have in common?

Answer 11

ADP ribosylation of Gs subunit of G-protein coupled receptor ▶️ (+) adenylate cyclase ▶️ secretion of fluid and electrolytes from intestinal epithelium

Question 12

Which bacteria possesses a three-component toxin?

Answer 12

Bacillus anthracis

*The anthrax toxin is the only medically important three-component toxin. It has one binding component (the protective antigen) and two active components, one an adenylate cyclase toxin and the other the lethal factor.

Question 13

Most common cause of pneumonia in school age children

Answer 13

Mycoplasma pneumoniae

Question 14

Biofilm producers microorganisms

Answer 14

Staphylococcus epidermidis (catheter-related infections)
Staphylococcus mutans (dental plaque)

Question 15

Urease positive microorganisms

Answer 15

Proteus (all species, renal calculi)
Ureaplasma (renal calculi)
Nocardia
Cryptococcus
Helicobacter

*PUNCH (mnemonic)

Question 15

Catalase positive organisms, is a major problem in which disease?

Answer 15

All staphylococcus 
Pseudomonas aeruginosa 
Candida 
Aspergillus 
Enterobacteriaceae
- CGD

Question 16

Coagulase positive microorganisms

Answer 16

Staphylococcus aureus

Yersinia pestis