Slide Deck 1

Question 1

What can you do to differentiate between staphylococci and streptococci, which are both types of ____ bacteria?

Answer 1

Catalase test: staph is positive strep is negative (Gram-positive cocci)

Question 2

1-3% hospital admissions in the US acquire ____ infections. It is the leading cause of bloodstream, lower respiratory tract, and SSTIs. what are SSTIs?

Answer 2

skin and soft tissue infections

Question 3

Most staph infections are caused by ____ strains.

Answer 3

MRSA: methicillin-resistant staphylococcus aureus

Question 4

What are two distinguishing factors that differentiate Staphylococcus aureus from Syaph epidermidis and Staph saprophyticus?

Answer 4

1. B- hemolytic (Beta-bulb) –this means that it completely lyses RBCs, making things look yellow and translucent on media. 2. Coagulase positive (red sea is parting) 3. ferments mannitol (tall man)

Question 5

What is an opportunistic pathogen? Which of the staph counts?

Answer 5

An infectious microorganism that is normally a commensal or does not harm its host but can cause disease when the host’s resistance is low (immunocompromised). Staphylococcus aureus is NOT—will infect and kill immunocompetent people. Staph epidermidis IS.

Question 6

Where does staphylococcus aureus colonize?

Answer 6

Skin, nares, GI tract

Question 7

Recurrent carbuncle/furunculosis?

Carbuncle: A carbuncle is a painful lesion or swollen boils that occur in groups and are attached to one another through the skin.

Answer 7

Staphylococcus Aureus

Question 8

What are the two causes of impetigo? If it has exfoliatin, which is it?

Answer 8

Staphylococcus aureus and Streptococcus pyrogenes

S. aureus uses exfoliatin

S. pyrogenes happens super rapidly!

Question 9

Both are slides of healing bone, but the left shows a problem. What is it called, and what is the leading cause?

Answer 9

Left: Osteomyelitus (infection and inflammation of the bone), Staph aureus

Question 10

Can staph aureus cause infection without pus?

Answer 10

Yes, you can see staph aureus cellulitis: superficial spreading of infections via lymphatics – , cellulitis is infection of skin tissue immediately below the skin’s outer surface.

Question 11

I got some delicious hot food but got rapid onset diarrhea! What happened! What specific toxin is responsible!

Answer 11

S. Aureus food poisoning due to ingestion of preformed toxin.

There was up to 6 hours of incubation,

the toxin is “enterotoxin” and it is HEAT STABLE.

spontaneous recovery after 24 hours.

(T cell superantigen)

Question 12

What pathogen is responsible for scalded-skin syndrome? What is it called in neonates v. children?

Answer 12

Exfoliatin (A or B) secretion cleaves the superficial layers of the skin

Ritter’s disease: generalized exfoliative dermatitis of newborns

Toxi epidermal necrolysis/bulbous impetigo: children

Question 13

What is quorum sensing, and how does S. aureus achieve it?

Answer 13

Quorum sensing (QS) allows bacteria to restrict the expression of specific genes to the high cell densities at which the resulting phenotypes will be most beneficial.

uses the accessory gene regulator agr:

RNAIII is produced in mass quantitities when feedback is positive: a lot of exotoxins are produced, supporting abcess production

Question 14

What is Protein A?

Answer 14

binds to immunoglobulins to block opsonization by antibodies (Fcy), or to modify B cell development (Vh3)

Found on surface of Staph aureus

NO ANTIBODY RESPONSE TO PROTEIN A

Question 15

What do we give for MRSA patients, and what is the problem?

Answer 15

vancomycin

it has to begiven intravenously (poor absorption in GI)–got to be in the hospital

renal failure, and we’re having resistant infections (which are then spread by horizontal transfer)

it’s hard to get antibiotics into

Question 16

What is the most frequent cause of sepsis and meningitis in low-weight neonates?

Answer 16

Staphylococcus epidermidis

Question 17

How do we subdivide among the strep types?

Answer 17

Figure out hemolysis. If it’s alpha, it’s partial

If beta, it’s complete (this is Group A or Group B–distinguish via bacitracin sensitivity)

If it’s gamma, it’s no hemolysis

Question 18

How do we classify types of Strep pyrogenes?

Answer 18

By their M serotype

Question 19

15-40% sore throat cases of children (but really rare in adults) is because of?

Answer 19

Group A or Strep Pyrogenes

Question 20

sore throat + rash? what toxin

Answer 20

SCARLET FEVER

Strep Group A

unique because of Erythrogenic toxin, which is released and binds to TCR and cross-links with MHC class II receptor of APCs, triggering T cell prolfieration and cytokine storm

increases disease severity of GAS pharyngitis

Question 21

Person had a skin infection, and then progressed to signs of nephritis: edema, blood and protein in urine.

What is this called?

Answer 21

Acute streptococcal glomerulonephritis– you see immune complexes in glomeruli

(can also happen post staph, but less frequently)

Question 22

What does Streptolyosin O depend on?

Answer 22

It needs cholesterol! to bind to cell and form pores