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Streptococci Flashcards

1
Q

Group A Strep:

A

Streptococcus pyogenes (Group A Strep)

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2
Q

Group B Strep

A

Streptococcus agalactiae (Group B Strep)

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3
Q

Streptococci catalase:

A

Catalase negative

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4
Q

Streptococci media:

A

Requires complex media

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5
Q

Streptococci oxygen requirement:

A

Prefers anaerobic or carbon dioxide atmosphere

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6
Q

Streptococci morphology:

A

Gram-positive Cocci in pairs and chains

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7
Q

Features that distinguish S. pneumoniae from Enterococcus

A

P.I.C.S

Production of pneumolysin

Inhibited by Optochin - tested by placing a disc on agar

Capsule

Soluble in the presence of bile

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8
Q

Streptococci hemolysis:

A

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

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

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9
Q

Describe the process of Lancefield typing of Streptococci.

A

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

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10
Q

What determines the Lancefield group of streptococci?

A

Group specific carbohydrates carried on the surface of streptococcus organisms

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11
Q

5 Laboratory techniques for identification of streptococcus organisms:

A

Hemolysis

Catalase Test

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

Streptolysin O Antibody Detection

Lancefield Typing

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12
Q

Purpose of the PYR Test PYR.

A

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

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13
Q

Purpose of the Streptolysin O Antibody Detection

test.

A

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

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14
Q

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

A

S.A.I.N.T.E

Scarlet Fever 
Acute pharyngitis
Impetigo
Necrotizing Fasciitis 
Toxic Shock-like Syndrome
Erysipelas
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15
Q

How is acute pharyngitis caused by S. pyogenes transmitted?

A

Via respiratory droplets

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16
Q

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

A

Acute viral pharyngitis

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17
Q

Classic symptoms of acute pharyngitis caused by S. pyogenes

A

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

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18
Q

Name the 2 clinical hallmarks of Erysipelas.

A

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

Fever and lymphadenopathy with accompanying streptococcal pharyngitis

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19
Q

Name the clinical hallmarks of Impetigo.

A

Pyoderma - small, pus-filled lesions

Pustules with yellow crust form on the face or extremities

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20
Q

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

A

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

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21
Q

How does one contract impetigo?

A

Associated with trauma / insect bites

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22
Q

How does one contract scarlet fever?

A

Complication of streptococcal pharyngitis

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23
Q

5 Hallmark features of Scarlet Fever:

A

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

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24
Q

Hallmark features of Necrotizing Fasciitis:

A

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

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

Systemic toxicity

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25
Q

Hallmark features of Toxic Shock-like Syndrome:

A

Multisystem organ failure (heart, respiratory tract, kidney)

Cultures are positive for group A strep

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26
Q

What infection may accompany Necrotizing Fasciitis?

A

Toxic Shock-like Syndrome

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27
Q

What virulence factor causes Toxic Shock-like Syndrome?

A

Streptococcal pyrogenic exotoxins (SPE)

28
Q

Name two diseases that occur as sequelae to streptococcal infections

A

Rheumatic Fever

Acute Glomerulonephritis

29
Q

4 Hallmark features of Rheumatic Fever:

A

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

30
Q

4 Hallmark features of Acute Glomerulonephritis:

A

Edema, hypertension, hematuria, proteinuria

Immune-complex deposits in the glomeruli seen on kidney biopsy

31
Q

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

A

To prevent post-streptococcal sequelae

32
Q

Rheumatic Fever occurs following what streptococcal infection?

A

1-5 weeks after strep pharyngitis

33
Q

Acute Glomerulonephritis occurs following what streptococcal infection?

A

Occurs after skin / respiratory infection with strep

34
Q

Describe the mechanism of Acute Glomerulonephritis?

A

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

35
Q

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

A

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

36
Q

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

A

Antibodies to M protein activate complement and kill the bacteria

37
Q

What is the function of streptokinase?

A

Cleaves fibrinogen to fibrin

Facilitates S. pyogenes spread in infected tissues

38
Q

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

A

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

39
Q

Which streptolysin does the body make antibodies for?

A

Streptolysin O

40
Q

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

A

Strep toxic shock-like syndrome

The rash in scarlet fever “erythrogenic exotoxin”

41
Q

How do SPE toxins cause disease?

A

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

42
Q

True or false: SPE toxins are heat labile.

A

True

43
Q

What does a Rapid Detection Test result mean?

A

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.

44
Q

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

A

neonatal, pregnant

45
Q

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

A

First week of life

Presents with bacteremia, pneumonia, or meningitis

46
Q

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

A

After 1 week to 3 months of age

Presents with bacteremia and meningitis

47
Q

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

A

The infant has a lack of protective maternal antibody (IgG)

Sialic acid on polysaccharide capsule inhibits complement allowing organisms to multiply

48
Q

How is Group B Strep Infection Prevented?

A

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

49
Q

How can growth of GBS be selected for in culture?

A

Use of selective enrichment broth (LIM)

50
Q

Infections caused by Group C Strep:

A

Associated with veterinary infections

Pharyngitis in college age patients

Sepsis

51
Q

Infections caused by Group F Strep:

A

Associated with abscesses

52
Q

Infections caused by Group G Strep:

A

Pharyngitis

Sepsis in neonates and elderly

53
Q

Name the alpha-hemolytic streptococci

A

S. pneumoniae
Viridans Streptococci
Bovis Group Streptococcus

54
Q

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

A

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

55
Q

When is culture helpful for diagnosis of S. pneumoniae?

A

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

56
Q

Describe Clinical manifestations of S. pneumoniae.

A

Onset is abrupt

Patients usually have productive cough and chest pain (pleurisy)

57
Q

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

A

S. pneumoniae

58
Q

What are Predisposing conditions to S. pneumoniae?

A 
Alcoholism 
Diabetes mellitus 
Chronic lung disease 
Chronic renal disease 
Certain malignancies
59
Q

What are the Streptococcus pneumoniae Virulence Factors?

A

Polysaccharide capsule - prevents phagocytosis

Pneumolysin - damages ciliated cells and activates the alternative complement pathway

Alpha hemolysis

60
Q

Name the most important characteristic of Viridans streptococci.

A

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)

61
Q

Which Viridans streptococci causes dental caries?

A

S. mutans is a major cause of dental caries

62
Q

Major clinical manifestations of Bovis group strep?

A

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

63
Q

Name the species included in the Anginosus Group Strep

A

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

64
Q

Name the major clinical infections caused by Anginosus Group Strep

A

Abscess formation in deep tissue (most brain abscesses)

65
Q

_______ inhibits growth of S. Pneumoniae.

A

Optochin

66
Q

Where is S. agalactiae prior to causing neonatal disease?

A

Maternal colonization of the vagina or rectum

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