3.5

Question 1

𝛼 (alpha)

Answer 1

partial hemolysis and green discoloration of hemoglobin (viridans strep mostly in oral cavity)

Question 2

𝛽 (beta)

Answer 2

clear zone of complete hemolysis (GBS and GAS)

Question 3

gamma

Answer 3

no zone of clearing

Question 4

Species level classification

Answer 4

Biochemical reactions look for particular enzymes.

• DNA sequence is also used

Question 5

Suppurative (pus) diseases-

Answer 5

caused by direct damage by the organism

Question 6

Toxin-mediated diseases

Answer 6

caused by streptococcal exotoxins secreted in bloodstream.

Question 7

Non-suppurative sequelea (bold)

Answer 7

late manifestations-autoimmune

Question 8

M protein-

Answer 8

adhesin binds to keratinocytes (outer layer of skin) • Adherance to host tissue

Question 9

Hyaluronic acid (HA) capsule-

Answer 9

antiphagocytic

Question 10

Hyaluronidase-

Answer 10

(spreading factor)- allows S. pyogenes to

spread through tissues

Question 11

Streptolysin S and O-

Answer 11

hemolysins that lyse various host cells

• Pore forming toxin (red blood cells- 𝜷-hemolysis on blood agar)

Question 12

Erythrogenic toxins-

Answer 12

fever, neutropenia, rash of scarlet fever

• Mediated through IL-1

Question 13

Streptokinase-

Answer 13

binds human plasminogen

Question 14

M- protein

Answer 14

Functions:
• Binds to keratinocytes
• Prevents opsonization by complement
a) Bindsfibrinogen-inhibitsalternative complement pathway
b) Binds complement control protein-
inhibits formation of opsonins by complement cascade

Question 15

Hyaluronic acid (HA) capsule

Answer 15

Purpose: Antiphagocytic structure
• Camouflage against the immune system • HA is found in human connective tissue
• However, capsule interferes with adherence to epithelial cells
• Hyaluronidase secreted by bacteria can digest the capsule, and also allows S. pyogenes to spread through tissue.

Question 16

Streptokinase

Answer 16

Binds plasminogen- enzymatic conversion it to plasmin
• Plasmin coated GAS can degrade and spread through fibrin (blood clots) resulting in invasive disease
• Therapeutic use in treating blood clots

Question 17

Streptococcal pyrogenic exotoxins (SpeA, SpeB, and SpeC)

Answer 17

Cause rash associated with scarlet fever (toxin spreads through blood)

Question 18

SpeB

Answer 18

most abundant extracellular protein-

• cysteine protease- can degrade immunoglobulins and cytokines- prevents complement activation (degrades C3b)

Question 19

SpeA and SpeC are also

Answer 19

bacterial superantigens-

• non-specifically activate large subset of T-cells - causing Streptococcal toxic shock syndrome (STSS)

Question 20

Most common manifestations of GAS

Answer 20

Acute Pharyngitis, Pyoderma – GAS infection of skin (impetigo)

Question 21

Acute Pharyngitis (strep throat)

Answer 21

Most common in school age children (age 5-15 years) • 20% are carriers (asymptomatic) in phaynx during winter
• Nasal carriers are more contagious

Question 22

Pyoderma – GAS infection of skin (impetigo)

Answer 22

Most common in preschool children (more common in tropics)

Question 23

Suppurative Infections: (pus)

Answer 23

Upper respiratory tract:
• Acute Pharyngitis
• Scarlet Fever- (toxigenic strains)
Treatment: 10 days penicillin
Strawberry tongue

Question 24

Cellulitis GAS

Answer 24

Acute inflammatory process involving subcutaneous tissue-
• Redness, heat and tenderness
• Indistinct boarders
• Can rapidly progress to
septicemia

Question 25

Erysipelas

Answer 25

Superficial erythematous and edematous lesions • Spreads in the superficial lymphatics of the dermis • Rash is confluent, salmon red in color, sharply demarcated

Question 26

Impetigo

Answer 26

Infection of the epidermis

Question 27

Non-Suppurative Infections (autoimmune diseases) (GAS)

Answer 27

-Acute Rheumatic Fever (ARF) (only follows pharyngeal infections by rheumatogenic strains) -Acute Post Streptococcal Glomerulonephritis (APSGN) (follows pharyngeal or skin infections by nephritogenic strains)

Question 28

Acute Rheumatic Fever (ARF)

Answer 28

Hypersensitivity reaction caused by cross-reacting antibodies effecting heart, joints, skin and brain (autoimmune disease?) Pharynx is the only site of infection that is followed by ARF • 1-4 weeks post strep throat - can occur after asymptomatic infection • No more than 10% of people are susceptible

Question 29

Acute Post Streptococcal Glomerulonephritis

Answer 29

Typical age affected 2-12 years –following strep throat or impetigo 5-21 days before. • Incidence is rare (6-20:100,000 in Western Countries) • Only occurs with nephritogenic GAS strains (Type M 12 and 49 most common) • Caused when immune complex containing streptococcal antigens are deposited in affected glomeruli

Question 30

Most common symptoms:Acute Post Streptococcal Glomerulonephritis

Answer 30

Edema | • Gross hematuria (tea colored urine) • Hypertension

Question 31

S. pyogenes

Answer 31

necrotizing fasciitis

Question 32

S. agalactiae (aerobic)

Answer 32

Leading cause of neonatal sepsis and meningitis • Actually more common, though less notorious than GAS • Inhabit lower GI and female genital tracts • May be transferred to babies during birth • 15-40% of women are carriers • Screening at 35 and 37 weeks gestation • If positive- intrapartum antibiotics are given to mother • In adults with chronic diseases, also causes cellulitis, arthritis, and meningitis

Question 33

Group B Streptococci (GBS)

Answer 33

``` Polysaccharide capsule • Unlike HA capsule of GAS • Prevents opsonization and phagocytosis • Nine serotypes – Type III most prevalent in neonatal sepsis is USA • Poorly antigenic • Efforts to make protein-carbohydrate conjugate vaccine (like pneumococcal vaccine) ```

Question 34

Groups C and G streptococci-

Answer 34

Other 𝛃-hemolytic Streptococci | commensal bacteria, airway, skin, and digestive tract and female genital tract.

Question 35

S. dysgalactiae

Answer 35

“pyogenes-like”)- Causes bovine mastitis • Greek: dys- bad, galactiae-milk

Question 36

S. equi-

Answer 36

Strangles in horses

Question 37

Enterococci and non-enterococci

Answer 37

𝛼- or 𝛾-hemolytic Many Group D streptococci have been placed in the genus Enterococcus (e.g., Streptococcus faecalis = Enterococcus faecalis) • Other non-enterococcal Group D strains include S. bovis and S. suis “World’s Toughest Pathogenic Bacteria” • Grow in high salt concentrations and in detergents (bile) • Inhibited, not killed, by penicillin • Resistance to most antibiotics Antibiotic synergism required for effective killing, usually penicillin and an aminoglycoside Vancomycin resistant enterococci (VREs) • Low virulence, but untreatable • Transfer vancomycin resistance to staphylococci in a laboratory setting • Dalfopristin-Quinipristin combination • Linezolid and daptomycin effective

Question 38

Non-enterococcal Group D Streptococci

Answer 38

S. bovis, S. suis

Question 39

S. bovis

Answer 39

most common for human disease • Infects cows, sheep, other ruminants

Question 40

S. suis

Answer 40

``` (pigs to humans) • Subacute bacterial endocarditis • Affects abnormal heart valves • Bacteremia – colonic lesions • Colon cancer association • Does not grow in high salt • Most strains are killed by penicillin ```

Question 41

• Most common cause of subacute bacterial | endocarditis

Answer 41

Introduced into the blood stream through brushing, flossing, dental proceedures • Affects abnormal heart valves • Prophylaxis antibiotics prescribed to high-risk patients

Question 42

Subacute Bacterial Endocarditis

Answer 42

Bacterial infection on endocardium (cells lining the inside of the heart). Usually develops when abnormal valves or Heart disease is present