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Pharm Exam #3 > L30 - Schreckenberger - Streptococcus and Enterococcus > Flashcards

L30 - Schreckenberger - Streptococcus and Enterococcus Flashcards

1
Q

Compare and Contrast Staph vs Strep - Catalase?

A

Staph - catalase positive (bubble in presence of H2O2)

Strep - catalase negative

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2
Q

Compare and Contrast Staph vs Strep - colony structure?

A

Staph - cocci in clusters

Strep - cocci in pairs/chains

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3
Q

Compare and Contrast Staph vs Strep - medium for growth?

A

Staph - grows in minimal media

Strep - requires complex media

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4
Q

Compare and Contrast Staph vs Strep - optimal temperature?

A

For both staph and strep, they grow best between 35-37 Celsius

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5
Q

Compare and Contrast Staph vs Strep - environmental conditions?

A

Staph = aerobic environment preferred

Strep = anaerobic or CO2 atmosphere preferred

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6
Q

Compare and Contrast Staph vs Strep - color/appearance on agar?

A

Staph = off color/whitish

Strep = opaque

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7
Q

Streptococcus belongs to what family and has what 3 subsets?

A

Family = Streptococcaceae

3 groups = Pyogenic, pneumococci , viridans

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8
Q

What are 3 ways to classify strep?

A
  1. serologic properties - lancefield groups (letters of alphabet)
  2. hemolytic properties - beta/gamma/alpha
  3. biochem properties
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9
Q

How does hemolytic classification of streptococci work?

A

Looks at amount hemolysis in blood agar

Beta = complete hemolysis
Alpha = incomplete hemolysis
Gamma = no hemolysis
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10
Q

What are the 6 important species for strep?

A
  1. Streptococcus pyogenes (Group A)
  2. Streptococcus agalactiae (Group B)
  3. Other Beta hemolytic streptococci
  4. Viridans group streptococci
  5. Nutritionally Deficient streptococci
  6. Streptococcus pneumoniae
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11
Q

What are the clinical manifestations that can appear with Strep pyogenes infections?

A
  1. Acute Pharyngitis (strep throat)
  2. Impetigo
  3. Erysipelas
  4. Necrotizing Fasciitis
  5. Toxic-Shock like Syndrome
  6. Pueperal Sepsis

“7.” Scarlet Fever (is a complication of strep throat)

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12
Q

Describe Acute pharyngitis caused by s pyogenes

A

strep throat

transmitted by respiratory droplets

self limiting = will go away without antibiotics (but can result in sequelae)

Reoccurs b/c strep has different m proteins and antibiotics have an antibody to a specific m protein

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13
Q

Define Impetigo

A

localized skin disease that has a pustule with yellow crust that appears on face/extremities

associated with trauma/insect bites

seen in kids 2-5 yrs old

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14
Q

Define erysipelas

A

Spreading erythema (superficial reddening) that’s well demarcated

get fever and lymphadenopathy

lesions on face/legs often accompany strep throat

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15
Q

What is scarlet fever?

A

Complication of strep throat caused by eryrthrogenic toxin

typically spares the face

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16
Q

What are the clinical manifestations of scarlet fever?

A

Sore throat
Fever
Bright red tongue with a “strawberry” appearance
*Note: rash begins to fade 3-4 days after onset and desquamation begins

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17
Q

What is necrotizing fasciitis?

A

Strep infection in deep subcutaneous tissues at the fascia level (spreads along fascial planes)

There’s extensive destruction of muscle/fat

Mortality > 50%

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18
Q

Erysipelas and Impetigo affect what layer (skin, subcutaneous, or muscle)?

A

skin

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19
Q

What is the key clinical clue for necrotizing fasciitis?

A

Pain for necrotizing fasciitis is disproportionate to how it looks

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20
Q

What is toxic shock-like syndrome?

A

Multisystem organ failure (heart, respiratory tract, kidney)

SPE toxins are similar to Staph aureus TSST-1

Cultures are usually positive for group A strep (unlike staph toxic shock)

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21
Q

What is peuerperal sepsis?

A

After delivery/abortion

Organisms invade upper genital tract and cause a variety of symptoms

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22
Q

What are the 2 post-streptococcal sequelae (can occur if you don’t treat strep throat)?

A

Rheumatic Fever and Acute Glomerulonephritis

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23
Q

Describe Rheumatic Fever

A

Non-suppurative inflammatory disease that occurs 1-5 weeks after strep throat

Reoccurs in adulthood

Has characteristic cardiac lesions (Aschoff bodies) and valvular damage

Symptoms = Fever, carditis, subcutaneous nodules, chorea, polyarthritis

24
Q

Describe Acute glomerulonephritis

A

Edema, hypertension, hematuria, proteinuria

Occurs after skin / respiratory infection

Certain M types are “nephritogenic”

Antigen-antibody-complement complexes are deposited in glomeruli (seen on kidney biopsy)

25
Q

What are 4 forms of virulence associated with Strep pyogenes?

A
  1. Ability of the bacteria to adhere to the surface of the host cells
  2. Invade into the epithelial cells
  3. Avoid opsonization and phagocytosis
  4. Produce a variety of toxins and enzymes
26
Q

What are 4 key virulence factors associated with Strep pyogenes?

A

Streptococcal pyrogenic exotoxins

M protein

Streptolysins and Streptokinase

27
Q

What are Streptococcal pyrogenic exotoxins (SPE)?

A

3 distinct heat labile toxins (A, B, C)

Are “superantigens” that stimulate cytokine response leading to shock and organ failure

Strep toxic shock-like syndrome

Responsible for the rash in scarlet fever “erythrogenic exotoxin”

28
Q

How do Streptolysins and Streptokinase enhance pathogenesis of S pyogenes?

A

allow spread of bacteria in tissues

29
Q

How does M protein play a role in the virulence of S pyogenes?

A

binds epidermal cells and allows bacteria to survive (anti-phagocytic)

Degrades complement C3b

*Note: strains without M protein are AVIRULENT

30
Q

How do you treat strep pyogenes?

A

Penicillin /ampicillin/amoxacillin
Drug of choice
No resistance worldwide

Cephalosporins

Erythromycin (if there’s penicillin allergy)

31
Q

Streptococcus Agalactiae belongs to what group?

A

GBS…Group B Strep

32
Q

What are the 2 forms of GBS infections that affect neonates? Describe each

A

Early Onset neonatal disease = 1st week of life –> Bacteremia, pneumonia, or meningitis

Late onset neonatal disease = 1 week-3 months old –> Bacteremia with meningitis

33
Q

How does neonate GBS infection occur?

A

Maternal colonization of vagina or rectum exposes baby at delivery

Lack of protective maternal antibody

Sialic acid on polysaccharide capsule inhibits C’ allowing organisms to multiply

Thus…vaginal/rectal swabs are collected between 35-37 weeks gestation

34
Q

How is GBS treated?

A

Penicillin / ampicillin = drug of choice

Add gentamicin to enhance killing

For culture positive pregnant women during labor – penicillin / ampicillin to prevent neonatal disease (KNOW)

Clindamycin if penicillin allergy

35
Q

What are the limitations of Rapid Group A Detection kits (KNOW)

A

Good specificity but sensitivity is only 70%

If it’s positive you can be sure they have group a strep = good specificity

If it’s negative, it can still be there…false negative

So if you have a negative rapid antigen test you always do a backup culture

36
Q

Isolation of S. bovis from blood is associated with ______

A

carcinoma of colon

37
Q

The Strep Milleri group includes which 3 species of strep?

A

S. anginosus
S. constellatus
S. intermedius

*Note: these pyogenic bacteria are identified by characteristic caramel (butterscotch) odor when cultured on agar plates

38
Q

The nutritionally deficient streptococci include? Have what vitamin deficiency?

A

Abiotrophia
Granulicatella

*Vitamin B6 deficient

39
Q

A 7-year-old child presents with a fever, pain in his ankles, knees and wrist, and a new heart murmur. His mother said that he complained of a “sore throat” last month, but the symptoms resolved without taking him to the pediatrician. A rapid screening test for strep throat is negative. His most likely diagnosis is:

A

Rheumatic Fever

40
Q

Are strep pneumoniae gram + or -? what about catalase?

A

Gram positive

Catalase negative

41
Q

If you suspect strep pneumoniae, what tests do you run?

A

Always do both a sputum and blood culture

42
Q

How do you identify strep pneumoniae in the lab?

A

Gram stain
Agar plates
Optochin test
Bile solubility

43
Q

How do you identify strep pneumoniae from a gram stain?

A

Gram positive and lancet shaped diplococci (sometimes seen alone or in chains)

In csf = menigitis
In sputum = pneumonia

44
Q

How do you identify strep pneumoniae from an agar plate?

A

can be runny mucoid colony or have flat dime shaped morphology with indented centers

45
Q

What are the breakpoints for treating strep pneumoniae with penicillin?

A

If you give penicillin for meningitis, it won’t cross BBB well so a low MIC is needed (.06 or less) for it to be susceptible

If non-meningeal target – MIC can be as high as 2 (sepsis or pneumonia)

46
Q

What are alternatives to penicillin for strep pneumoniae?

A

If allergic…uses macrolides or fluoroquinolones

47
Q

What are the 2 major species of enterococci causing infection in humans?

A

E. Faecalis
E. Faecium

*enterococcus was formally group d streptococci

They are inherently resistant to many commonly used antibiotics

48
Q

Are enterococci gram + or -?

A

Gram positive

49
Q

What is PYR?

A

used in testing for enterococci, which are PYR positive (get a red color)

50
Q

What infections are seen with enterococci?

A

Urinary tract
Mixed bacterial wound infections and decubiti
Sepsis, endocarditis, meningitis (rare)
Second most common nosocomial pathogen

51
Q

Where is enterococci found and how is it spread?

A

Originates in flora of bowel
Transferred between patients
Acquired thru consumption of contaminated food/water

52
Q

What is VRE?

A

Vancomycin Resistant Enterococci

53
Q

What are the 3 VRE phenotypes?

A

A - plasmid mediated, highly resistant
B - chromosomal, high or low resistance
C - intrinsic intermediate level in E. gallinarum and casseliflavus (casseliflavus = yellow colonies)

*Treat via linezolid

54
Q

How are enterococcal infections treated? (know!)

A

Intrinsically resistant to all cephalosporins, trimethoprim-sulfa, aminoglycosides

Faecalis is susceptible to penicillin/amp
Faecium is resistant to penicillin/amp

55
Q

An organism is isolated from the blood of a 65 year-old male patient with a diagnosis of probable bacterial endocarditis. The organism displays streptococcus-like morphology on gram stain and is catalase-negative. On blood agar the colonies appear gamma hemolytic and are PYR positive. Patient was being treated with vancomycin plus an aminoglycoside with no response. This isolate is likely to be ____ species

A

Enterococcus

Pharm Exam #3 (5 decks)

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