Chapter 5: Staphylococci

Question 1

What are the three major pathogenic species of Staphylococci?

Answer 1

Staph aureus, epidermidis, and saprophyticus

Question 2

What are the three tests that can differentiate Staphylococci from streptococci?

Answer 2

Gram stain
Catalase test
Culture

Question 3

How does staph compare to strep in a gram stain?

Answer 3

Staph are in clusters with a golden appearance (aureus)

Strep are found in a line like candy buttons

Question 4

How does staph compare to strep in a catalase test?

Answer 4

All staphylococci have catalase
Rub wire loop across a colony of gram-positive cocci and mix on a slide with H2O2
Bubbles = catalase
Strep does NOT have catalase

Question 5

How does Staph compare to Strep in a culture?

Answer 5

Staph aureus can be differentiated from other beta-hemolytic strep by its golden pigment on sheep blood agar

Question 6

What is the ONLY Staphylococcus that is coagulase positive? what does this mean?

Answer 6

Staphylococcus aureus
Activates prothrombin causing blood to clot
Leads to fibrin formation around the bacteria

Question 7

What proteins of Staphylococcus aureus disable our immune system?

Answer 7

Protein A 
Coagulase
Hemolysins
Leukocidins
Penicillinase
Novel penicillin binding protein/transpeptidase

Question 8

What does Protein A do?

Answer 8

Site that binds to Fc portion of IgG

May protect the organism from opsonization and phagocytosis

Question 9

What is the role of hemolysins?

Answer 9

4 types - alpha, beta, gamma and delta

Destroy RBC, neutrophils, Mo and platelets

Question 10

What is the role of leukocidins?

Answer 10

destroy leukocytes (WBCs)

Question 11

What particular leukocidin does CA-MRSA produce?

Answer 11

Panton-Valentine Leukocidin (PVL) - associated with a propensity to form abscesses

Question 12

What is Novel penicillin binding protein?

Answer 12

Necessary for cell wall peptidoglycan formation and is inhibited by penicillin

Question 13

What proteins released by Staphylococcus aureus tunnel through tissue?

Answer 13

Hyaluronidase: breaks down proteoglycans in CT
Staphylokinase: lyses formed fibrin clots
Lipase: Degrades fats and oils
Protease: destroys tissue proteins

Question 14

What protein facilitates Staphylococcus aureus’ colonization of sebaceous glands?

Answer 14

Lipase

Question 15

What is the exotoxin assault weaponry of Staphylococcus aureus?

Answer 15

Exfoliatin
Enterotoxins
TSST-1

Question 16

What is the role of exfoliatin?

Answer 16

Diffusible exotoxin that causes skin to slough off

Scalded skin syndrome

Question 17

Toxic Shock Syndrome Toxin

Answer 17

Analogous to the pyrogenic toxin produced by Lancefield Group A beta-hemolytic streptococci, but far more deadly

Bind MHC class II molecules on APCs, causes T cell response and outpouring of cytokines

Question 18

What are the diseases caused by exotoxin release from Staphylococcus aureus ?

Answer 18

Gastroenteritis (food poisoning): growth in food, peristalsis of the intestine leading to nausea, vomiting, diarrhea, abdominal pain, and fever 12-24 hrs

TSS: tampons, stimulate TNF and IL-1

Scalded skin syndrome: Exfoliative toxin A and B, localized infection and releases diffusible toxin that exerts distant effects,

Question 19

Who does Scalded Skin Syndrome mostly affect?

Describe what clinically happens

Answer 19

Neonates with local infection of the recently severed umbilicus or older children with skin infections

Causes cleavage of the middle epidermis with fine sheets of skin peeling off to reveal moist red skin beneath
Healing rapid

Question 20

What are the diseases resulting from direct organ invasion of Staphlycoccus aureus?

Answer 20

Pneumonia
Meningitis
Osteomyelitis 
Acute bacterial endocarditis 
Septic arthritis
Skin infections
Bacteremia/sepsis 
Urinary tract infection

Question 21

Staphylococcus aureus and pneumonia

Answer 21

Rare but severe cause of CA-bacterial pneumonia
More common in hospitalized pts
Usually follows viral flu
Abrupt onset of fever, chills, and lobar consolidation of the lung, rapid destruction of the lung parenchyma
Effusions and empyema

Question 22

Osteomyelitis

Answer 22

bone infection that usually occurs in boys under 12 yrs of age
Infection spreads to the bone hematogenously,
Warm, swollen tissue over the bone and with systemic fever and shakes

Caused by Staph aureus

Question 23

What is the most common pathogen causing Septic arthritis in pediatric age group and in adults over the age of 50

Answer 23

Staph Aureus

Question 24

Minor skin infections are almost exclusively caused by what?

Answer 24

Either Strep pyogenes or Staph aureus

Question 25

What are the skin infections caused by Staph or strep ?

Answer 25

Impetigo: contagious, on face, small vesicles lead to pustules, crust over honey-colored, wet, and flaky
Cellulitis: Deeper infection of cells, red, hot shiny swollen
Local abscesses, Furuncles, and carbuncles
Wound infection: results in abscess, cellulitis or both

Question 26

What is an abscess, furuncle and carbuncle?

Answer 26

Abscess: collection of pus
Furuncle: Infection can penetrate deep into subcutaneous tissue
Carbuncles: infection bore through to produce multiple contiguous, painful lesions communicating under the skin

Question 27

Blood and catheter infections by staph aureus can result in what?

Answer 27

bacteremia, sepsis, septic shock,and endocarditis

Question 28

What is a common skin contaminant of blood cultures?

Answer 28

Staph epidermidis

Question 29

Staphylococcus epidermidis

Answer 29

Normal bacterial flora and is widely found in our body, coagulase-negative
Infections of prosthetic devices in the body

Question 30

Biofilms

Answer 30

Staph epidermidis often form these on intravascular catheters and leaches out to cause bacteremia and catheter related sepsis

Question 31

Staphylococcus saprophyticus

Answer 31

Leading cause (second only to E.coli) of urinary tract infections in sexually active young women