Streptococci

Question 1

Group A Strep:

Answer 1

Streptococcus pyogenes (Group A Strep)

Question 2

Group B Strep

Answer 2

Streptococcus agalactiae (Group B Strep)

Question 3

Streptococci catalase:

Answer 3

Catalase negative

Question 4

Streptococci media:

Answer 4

Requires complex media

Question 5

Streptococci oxygen requirement:

Answer 5

Prefers anaerobic or carbon dioxide atmosphere

Question 6

Streptococci morphology:

Answer 6

Gram-positive Cocci in pairs and chains

Question 7

Features that distinguish S. pneumoniae from Enterococcus

Answer 7

P.I.C.S

Production of pneumolysin

Inhibited by Optochin - tested by placing a disc on agar

Capsule

Soluble in the presence of bile

Question 8

Streptococci hemolysis:

Answer 8

beta hemolytic: GAS, GBS, anginosus, groups C and G

alpha hemolytic: enterococci, viridans, anginosus, S. pneumoniae

Question 9

Describe the process of Lancefield typing of Streptococci.

Answer 9

Latex Agglutination Assay:

Beaded, individual antibodies are added to a carbohydrate on the surface of the colonies on agar

If there is a carbohydrate-specific interaction, there is clumping specific to the Lancefield group

Question 10

What determines the Lancefield group of streptococci?

Answer 10

Group specific carbohydrates carried on the surface of streptococcus organisms

Question 11

5 Laboratory techniques for identification of streptococcus organisms:

Answer 11

Hemolysis

Catalase Test

PYR Test PYR (L-pyrrolidonyl-ß- naphthylamide)

Streptolysin O Antibody Detection

Lancefield Typing

Question 12

Purpose of the PYR Test PYR.

Answer 12

Quick spot test for detection of pyrrolidonyl peptidase enzyme and the identification of Enterococcus and Group A strep

Question 13

Purpose of the Streptolysin O Antibody Detection

test.

Answer 13

Useful for confirming a diagnosis of rheumatic fever following production of antibodies to Streptolysin O 3-4 weeks after initial exposure to S. pyogenes

Question 14

What are the 6 of Streptococcus pyogenes infections discussed in lecture?

Answer 14

S.A.I.N.T.E

Scarlet Fever 
Acute pharyngitis
Impetigo
Necrotizing Fasciitis 
Toxic Shock-like Syndrome
Erysipelas

Question 15

How is acute pharyngitis caused by S. pyogenes transmitted?

Answer 15

Via respiratory droplets

Question 16

Acute pharyngitis caused by S. pyogenes presents very similarly to what infection?

Answer 16

Acute viral pharyngitis

Question 17

Classic symptoms of acute pharyngitis caused by S. pyogenes

Answer 17

Fever
Sore throat
Headache
Cervical lymphadenopathy (swollen lymph nodes), Peritonsillar exudate

Question 18

Name the 2 clinical hallmarks of Erysipelas.

Answer 18

Spreading erythema and lesions often with well demarcated edge on the face (or legs)

Fever and lymphadenopathy with accompanying streptococcal pharyngitis

Question 19

Name the clinical hallmarks of Impetigo.

Answer 19

Pyoderma - small, pus-filled lesions

Pustules with yellow crust form on the face or extremities

Question 20

State the demographic most affected by impetigo and the reason why.

Answer 20

Affects young children, usually in the warm months and as a result of poor hygiene

Question 21

How does one contract impetigo?

Answer 21

Associated with trauma / insect bites

Question 22

How does one contract scarlet fever?

Answer 22

Complication of streptococcal pharyngitis

Question 23

5 Hallmark features of Scarlet Fever:

Answer 23

Fine, red, and rough-textured rash, but not on face followed by desquamation

Circumoral pallor

Sore throat - exudate over tonsillar area of throat

Fever

Bright red tongue with a “strawberry” appearance

Question 24

Hallmark features of Necrotizing Fasciitis:

Answer 24

Occurs deep in the subcutaneous tissues and spreads along the fascial planes.

Extensive destruction of the muscle and fat
(flesh-eating)

Systemic toxicity

Question 25

Hallmark features of Toxic Shock-like Syndrome:

Answer 25

Multisystem organ failure (heart, respiratory tract, kidney) Cultures are positive for group A strep

Question 26

What infection may accompany Necrotizing Fasciitis?

Answer 26

Toxic Shock-like Syndrome

Question 27

What virulence factor causes Toxic Shock-like Syndrome?

Answer 27

Streptococcal pyrogenic exotoxins (SPE)

Question 28

Name two diseases that occur as sequelae to streptococcal infections

Answer 28

Rheumatic Fever | Acute Glomerulonephritis

Question 29

4 Hallmark features of Rheumatic Fever:

Answer 29

F.E.N.A Non-suppurative inflammatory disease Fever, carditis, subcutaneous nodules, chorea, polyarthritis Aschoff bodies - characteristic cardiac lesions and valvular damage Endocarditis later in life

Question 30

4 Hallmark features of Acute Glomerulonephritis:

Answer 30

Edema, hypertension, hematuria, proteinuria Immune-complex deposits in the glomeruli seen on kidney biopsy

Question 31

Why are Strep infections (i.e. streptococcal pharyngitis) treated?

Answer 31

To prevent post-streptococcal sequelae

Question 32

Rheumatic Fever occurs following what streptococcal infection?

Answer 32

1-5 weeks after strep pharyngitis

Question 33

Acute Glomerulonephritis occurs following what streptococcal infection?

Answer 33

Occurs after skin / respiratory infection with strep

Question 34

Describe the mechanism of Acute Glomerulonephritis?

Answer 34

M protein antigen-antibody complexes activate complement, which results in immune-complex deposits in the glomeruli

Question 35

Describe M protein's 3 mechanisms of virulence for S. pyogenes.

Answer 35

Assists in binding to epidermal cells Allows bacterial survive (Strains without M protein are avirulent) Anti-phagocytic: Degrades complement C3b to prevent opsonization and killing by phagocytosis

Question 36

Antibodies to ___ _________ activate complement and kill S. pyogenes.

Answer 36

Antibodies to M protein activate complement and kill the bacteria

Question 37

What is the function of streptokinase?

Answer 37

Cleaves fibrinogen to fibrin Facilitates S. pyogenes spread in infected tissues

Question 38

What are the functions of S. pyogenes streptolysins? Name the 2 types.

Answer 38

Lyse RBCs and leukocytes Cause the death of phagocytic cells Assists in spread of bacteria in tissues Streptolysin S and Streptolysin O

Question 39

Which streptolysin does the body make antibodies for?

Answer 39

Streptolysin O

Question 40

What clinical manifestations of strep infections are due to SPE toxins?

Answer 40

Strep toxic shock-like syndrome The rash in scarlet fever “erythrogenic exotoxin”

Question 41

How do SPE toxins cause disease?

Answer 41

They are "superantigens” that cause non-specific activation of T-cells, T cell proliferation and cytokine release leading to massive shock and organ failure.

Question 42

True or false: SPE toxins are heat labile.

Answer 42

True

Question 43

What does a Rapid Detection Test result mean?

Answer 43

If a Rapid Group A Detection Test is positive, in correlation with the clinical symptoms, you can be certain that the patient is infected with a Group A strep.

Question 44

S. agalactiae is a common cause of _______ disease and infection in _______ women.

Answer 44

neonatal, pregnant

Question 45

When does early onset-neonatal disease present and with what clinical manifestations?

Answer 45

First week of life Presents with bacteremia, pneumonia, or meningitis

Question 46

When does late onset-neonatal disease present and with what clinical manifestations?

Answer 46

After 1 week to 3 months of age Presents with bacteremia and meningitis

Question 47

Describe virulence of S. agalactiae and how it causes neonatal disease.

Answer 47

The infant has a lack of protective maternal antibody (IgG) Sialic acid on polysaccharide capsule inhibits complement allowing organisms to multiply

Question 48

How is Group B Strep Infection Prevented?

Answer 48

Cultures should be performed on BOTH vaginal/rectal swabs collected at 35 to 37 weeks gestation to identify if there is colonization with GBS. If colonized, mother will receive prophylatic antibiotics to prevent infection in the baby

Question 49

How can growth of GBS be selected for in culture?

Answer 49

Use of selective enrichment broth (LIM)

Question 50

Infections caused by Group C Strep:

Answer 50

Associated with veterinary infections Pharyngitis in college age patients Sepsis

Question 51

Infections caused by Group F Strep:

Answer 51

Associated with abscesses

Question 52

Infections caused by Group G Strep:

Answer 52

Pharyngitis | Sepsis in neonates and elderly

Question 53

Name the alpha-hemolytic streptococci

Answer 53

S. pneumoniae Viridans Streptococci Bovis Group Streptococcus

Question 54

How does S. pneumoniae get into the respiratory tract to cause disease.

Answer 54

Normal flora of human upper respiratory tract. Usually causes disease after aspiration, so bacteria are inhaled into the lung and multiply in alveolar spaces

Question 55

When is culture helpful for diagnosis of S. pneumoniae?

Answer 55

Culture can be helpful in patients that are immunocompromised or have severe disease, but not in patients who have community-associated pneumonia

Question 56

Describe Clinical manifestations of S. pneumoniae.

Answer 56

Onset is abrupt | Patients usually have productive cough and chest pain (pleurisy)

Question 57

_______ is the most common cause of community acquired acute bacterial pneumonia.

Answer 57

S. pneumoniae

Question 58

What are Predisposing conditions to S. pneumoniae?

Answer 58

``` Alcoholism Diabetes mellitus Chronic lung disease Chronic renal disease Certain malignancies ```

Question 59

What are the Streptococcus pneumoniae Virulence Factors?

Answer 59

Polysaccharide capsule - prevents phagocytosis Pneumolysin - damages ciliated cells and activates the alternative complement pathway Alpha hemolysis

Question 60

Name the most important characteristic of Viridans streptococci.

Answer 60

Alpha or gamma hemolytic Lacks hemolysins and toxins of beta strep Normal flora of upper respiratory tract Opportunistic pathogen causing sepsis, especially in neutropenic cancer patient Important cause of endocarditis (primary presentation)

Question 61

Which Viridans streptococci causes dental caries?

Answer 61

S. mutans is a major cause of dental caries

Question 62

Major clinical manifestations of Bovis group strep?

Answer 62

carcinoma of colon bacteremia, meningitis both native and prosthetic-valve endocarditis

Question 63

Name the species included in the Anginosus Group Strep

Answer 63

S. anginosus, S. constellatus, S. intermedius (Group C, F, G, U)

Question 64

Name the major clinical infections caused by Anginosus Group Strep

Answer 64

Abscess formation in deep tissue (most brain abscesses)

Question 65

_______ inhibits growth of S. Pneumoniae.

Answer 65

Optochin

Question 66

Where is S. agalactiae prior to causing neonatal disease?

Answer 66

Maternal colonization of the vagina or rectum