Staphylococcus

Question 1

Gram and shape of Staphylococcus species

Answer 1

gram positive cocci arranged in clusters
resemble grapes

Question 2

Metabolism of Staphylococcus species

Answer 2

facultative anaerobe but able to thrive in both conditions

Question 3

Catalase test for Staphylococcus species

Answer 3

catalase (+)
provides ROS resistance

Question 4

Coagulase test for Staphylococcus species

Answer 4

S. aureus is the only coagulase (+) staph
best way to differ

Question 5

S. auerus key features and diseases

Answer 5

Golden/yellow colonies on agar
Causes
S.S.S. TSS, Food poisoning, suppurative infections

Question 6

S.epidermidis key features & diseases

Answer 6

outer skin
normal flora
wound infections, cathers, and prosthetic device infections

Question 7

S. saprophyticus key features & diseases

Answer 7

UTIs in newly sexually active women

Question 8

S. lugdunensis and S. haemolyticus

Answer 8

causes skin infection similar to aureus
and
frequently involved in wound infections

Question 9

Toxin mediated diseases by S. aureus

Answer 9

Scalded Skin Syndrome, Food posioning, and TSS

Question 10

Toxin mediated diseases | Scalded skin syndrome

Answer 10

Desquamation [shedding] of epithelium
Infants
exfoliative toxins [EF-A, ET-B]

Question 11

Toxin mediated | Food Posioining

Answer 11

Rapid onset vomiting and diarrhea. No fever.
resolves in 24 hours
Enterotoxins

Question 12

Exfoliative toxins

Answer 12

ET-A is phage associated
and ET-B is plasmid associated

Question 13

Toxic shock syndrome toxin 1

Answer 13

Superantigen that causes a cytokine storm

penetrates mucosal barriers, causing a systemic immune response

Includes excessive release of TNF-a IL-1, and INF

Question 14

Suppurative infections of S. aureus

Answer 14

impetigo, furuncles/boils, carbuncles, bacteremia/endocarditis, osteomyelitis, pneumonia, and septic arthritis

Question 15

Impetigo, furuncles/boils, carbuncles, and bacteremia

Answer 15

Impetigo: localized cutaneous infection characterized by pus filled vesicles

folliculitis: infection of hair follicles

furuncles/boils: large, painful pus filled nodules

Bacteremia: bacteria in blood

Question 16

Endocarditis, osteomyelitis, pneumonia, and septic arthritis

Answer 16

E - infect hear valves
Ost- bone infection
Pn- lung consolidation and abscess formation
S.A - joint infection

Question 17

Suppurative infection have what inside their pus

Answer 17

neutrophils and M0

Question 18

Virulence factors of S. aureus

Answer 18

Capsule - inhibits chemotaxis, phagocytosis, and proliferation of immune cells

slime layer - facilitates adherence to foreign bodies

peptidoglycan - osmotic stability for bacteria, triggers pyrogen production [fever inducing], chemoattract, abscesses formation

Teichoic acid - binds to fibronectin

Protein A - inhibits antibody mediated clearance by binding to fc region of IgG | inhibiting opsonization and complement

Question 19

Cytotoxins [alpha, beta, delta, gamma]

Answer 19

Toxic to alot of cell types
causes cell lysis

ex. a toxin forms pores in membranes

Question 20

Exfoliative toxins [ET-A and ET-B]

Answer 20

Serine proteases that spilt the intercellular bridges in the granuloma epidermis [blisters]

Question 21

Enterotoxins [A-E,G-I] Toxins

Answer 21

Superantigens that cause food poisoning
stimulate t cells and cytokine release

Question 22

TSST-1 Toxins

Answer 22

Superantigen that causes TSS by including cytokine storms

Question 23

Coagulase Enzyme

Answer 23

converts fibrinogen to fibrin

Question 24

Hyaluronidase

Answer 24

hydrolyzes hyaluronic acid, allowing spread in tissues

Question 25

Fibrinolysin

Answer 25

dissolves fibrin clots

Question 26

Lipases

Answer 26

hydrolyzes lipids

Question 27

Nucleases

Answer 27

hydrolyzes DNA

Question 28

Alpha toxin

Answer 28

S. aureus, pore forming, osmolysis, RBC, platelets

Question 29

Beta Toxin

Answer 29

S. aureus sphingoelinase C [lipase], RBC marcophages, leukcytes

Question 30

Y-toxin

Answer 30

pore forming leukotoxic, hemolytic,

Question 31

&-toxin

Answer 31

Staph spp
surfactant activity disrupts membranes

Question 32

P-V Leukocidins

Answer 32

pore forming
6 flavors
leukotoxic not hemolytic

Question 33

What signaling molecules are involved in quorum sensing?

Answer 33

AIP1-4
bind to apolipoprotein B which helps reduce toxin production by bacteria

Question 34

S. Aureus and Quorum sensing

Answer 34

Q. sensing allows bacteria to sense their population density

low? no toxins off
High? toxins on

Question 35

MRSA Methicillin resistance is caused by

Answer 35

Altered penicillin binding proteins PBP2A [originally just PBP]

Question 36

What’s encodes for the altered PBP2A protein?

Answer 36

mecA gene

Question 37

How does VRSA or vancomycin resistance occur?

Answer 37

Alterations in peptidoglycan synthesis [the vanA gene]

Question 38

What’s important about the microscopy of S. aureus ?

Answer 38

Has to be from base of localized lesion. Pus may not have alot of organisms

Question 39

Diagnosis method of Staph Aureus

Answer 39

Microscopy - from base of localized lesions
Coagulase Test - [blood clot = (+) | no blood clot (-)]
Mannitol salt agar - [turns yellow]
Nucleic acid based test - detect MRSA genes mecA