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NPLEX - Micro/Immuno > Gram-positive cocci > Flashcards

Gram-positive cocci Flashcards

1
Q

What lab findings are useful to help diagnose Strep. pneumoniae?

A

spinal tap cloudy w/ increase in PMNs and low glucose

lancet-shaped gram+ cocci

alpha-hemolytic on blood agar

inhibited by optochin

older cells may appear gram-

lysed by bile

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2
Q

Identify the major virulence/toxicity factor associated with Staph. saprophyticus.

A

novobiocin resistant

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3
Q

How is Strep. agalactiae (group B strep) transmitted?

A

during childbirth from mother to infant

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4
Q

Identify the major virulence/toxicity factor associated with Strep. viridans.

A

destran biofilm-mediated adhesion to teeth and heart valves

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5
Q

What is the morphology of Group D Strep./Enterococcus?

A

cocci

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6
Q

Name some pyogenic manifestations of Strep. pyogenes.

A

pharyngitis, cellulitis, impetigo

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7
Q

When do you test for bacitracin sensitivity or resisitance?

A

to distinguish beta-hemolytic strep.

bacitracin-sensitive suggests GABHS (strep. pyogenes)

bacitracin-resistant suggests GBBHS (strep. agalactiae)

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8
Q

What organisms are beta hemolytic?

A

Staph. aureus, Strep. pyogenes, Strep. agalactiae, Lysteria monocytogenes

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9
Q

Identify the major virulence/toxicity factors associated with Strep. pyogenes (GABHS).

A

erythrogenic toxin may lead to scarlet fever which can progress to rheumatic fever

hyaluronic acid capsule in non-immunogenic, inhibiting phagoctyic uptake

M-protein is antiphagocytic

M12 strains associated with acute glomerulonephritis

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10
Q

Staph. aureus is catalase __ and coagulase __.

A

+

+

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11
Q

Viridans strep are catalase __ and optochin __.

A

sensitive

resistant

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12
Q

How does Strep. agalactiae gram stain?

A

+

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13
Q

T/F: enterococci (group D strep.) are penicillin G sensitive and show variable hemolysis

A

F - they are resistant but do have variable hemolysis

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14
Q

What is the “most common” associated with Strep. agalactiae?

A

neonatal sepsis and meningitis

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15
Q

What are catalase and coagulase tests used for?

A

Catalase is used to distinguish staph (+) from strep (-)

Coagulase is used to distinguish S. aureus (+) from S. epidermis and S. saprophyticus (-)

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16
Q

How does Strep. pneumoniae gram stain?

A

+

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17
Q

What is the morphology of Strep. pneumoniae?

A

cocci

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18
Q

What lab findings are useful to help diagnose Staph. saprophyticus?

A

+ growth on blood agar

+ catalase

+ gamma hemolysis

+ novobiocin resistance

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19
Q

Strep. pyogenes is catalase __ and bacitracin __.

A

negative

sensitive

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20
Q

What is the second leading cause of UTIs in sexually active women?

A

Staph. saprophyticus

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21
Q

What are the clinical manifestations of Strep. pneumoniae?

A

pneumonia, meningitis, bacteremia, OM, sinusitis

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22
Q

What lab findings are useful to help diagnose Staph. epidermidis?

A

gram + cocci arranged in clusters

catalase +

coagulase -

no hemolysis

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23
Q

What is the “most common” associated with Strep. pneumoniae?

A

bacterial pneumonia in adults

meningitis

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24
Q

What lab findings are useful to help diagnose Strep. pyogenes?

A

beta hemolysis +

susceptible to bacitracin

rapid antigen strep test

gram + cocci in chains

catalase -

ASO titer for rheumatic fever

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25
Q

Does Staph. aureus gram stain positive or negative?

A

+

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26
Q

Staph. aureus: TSST is a superantigen that binds to __ and __ receptors. This causes __ of T cells, leading to toxic shock syndrome.

A

MHC II

T-cell receptors

polyclonal activation of T-cells

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27
Q

What is the major reservoir for Strep. agalactiae?

A

normal flora of female genital tract
GI tract

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28
Q

What is the morphology of Strep. pyogenes?

A

cocci in chains or pairs

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29
Q

Name some key lab findings that are useful to help diagnose Staph. aureus.

A

gram+

yellow, grape-like clusters on blood agar

beta-hemolytic

catalase +

coagulase +

salt tolerant

ferments mannitol (s. epidermidis cannot)

Facultative anaerobe

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30
Q

Identify the major virulence/toxicity factors associated with Strep. agalactiae.

A

penicillin resistant

encapsulated

beta-hemolysin

CAMP factor

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31
Q

List the SSx of rheumatic fever.

A

polyarthritis, erythema marginatum, chorea, carditis, subQ nodules

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32
Q

Identify the major virulence/toxicity factor associated with Strep. pneumoniae.

A

can make over 85 antigenically distinct capsular polysaccharides, which can interfere with phagocytosis.

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33
Q

Identify four major virulence/toxicity factors associated with Staph. aureus.

A

protein A inhibits phagocytosis, binds Fc portion of antibody
- Bind Fc region on IgG → ↓ Complement activation → ↓ C3b

enterotoxins A-E are heat stable

TSST-1 causes TSS

coagulases convert fibrinogen to a fibrin clot

exfoliatins cause scalded skin syndrome

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34
Q

What is the morphology of Staph. epidermidis?

A

cocci

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35
Q

Strep. pneumococci are catalase __ and optochin __.

A

-

sensitive

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36
Q

What are the “most commons” associated with Strep. pyogenes?

A

pharyngitis

cellulitis

erysipelas in children

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37
Q

What are the clinical manifestations of Strep. agalactiae?

A

acute lower UTI (uncommon)

neonatal pneumonia

sepsis

meningitis

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38
Q

What is the morphology of Staph. saprophyticus?

A

cocci

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39
Q

What are the clinical manifestations of Staph. saprophyticus?

A

UTIs, esp. in young sexually active women

Sx: dysuria, hematuria, frequent urination, burning urination and urgency

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40
Q

What lab findings are useful to help diagnose Strep. viridans?

A

alpha-hemolytic

resistant to optochin

gram+ cocci in chains

bile resistant

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41
Q

Staph. aureus: What is the function of protein A?

A

virulence factor - binds to Fc-IgG and inhibits complement fixation and phagocytosis

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42
Q

How is Strep. pneumoniae transmitted?

A

respiratory drops

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43
Q

Does Staph. aureus ferment lactose?

A

no

44
Q

T/F: S. aurues causes skin disease and organ abscesses, but not pneumonia

A

F - causes all 3

45
Q

How does Staph. saprophyticus gram stain?

A

+

46
Q

What are the pyogenic, immunologic and toxigenic clinical manifestations of Strep. pyogenes?

A

pyogenic (pharyngitis, impetigo, cellulitis, erysipelas)

immunogenic (glomerulonephritis, erythema nodosum, rheumatic fever, rheumatic heart disease)

toxigenic (scarlet fever, purperal fever)

47
Q

Identify the major virulence/toxicity factors associated with Staph. epidermidis.

A

highly antibiotic resistant (PSM peptide toxin)

can form biofilm and adhere to surfaces like catheters

48
Q

What is the major reservoir for Strep. pneumoniae?

A

human upper respiratory tract

49
Q

How does Strep. viridans gram stain?

A

+

50
Q

What are the clinical manifestations of Staph. epidermidis?

A

prosthetic, surgical and wound infections (nosocomial) especially in the immunocompromised patient

inflammation at site of infection, fever, fatigue

51
Q

How does Staph. epidermidis gram stain?

A

+

52
Q

Viridans strep are __ hemolytic

A

alpha

53
Q

Identify relevant epidemiology and risk factors associated with Staph. aureus.

A

surgery or any break in the skin

severe neutropenia

IV drug abuse

chronic granulomatous disease

54
Q

How is Staph. aureus transmitted?

A

hands and sneezing

surgical wounds

contaminated foods, esp. home canned meats, potato salad

55
Q

Name three toxins of S. aureus and a syndrome caused by each.

A

TSST-1 (TSS)

exofoliative toxin (scalded skin syndrome)

enterotoxins (rapid onset food poisoning)

56
Q

How does group D Strep/enterococcus gram stain?

A

+

57
Q

What lab findings are useful to help diagnose Strep. agalactiae?

A

catalase -

beta-hemolytic on blood agar

bacitraicin resistant

CAMP+ (indicates group B)

hydrolyzes hippurate

58
Q

What organisms are alpha-hemolytic?

A

strep. pneumoniae

strep. viridans

59
Q

T/F: S. aureus causes acute bacterial endocarditis.

A

T

60
Q

Strep agalactiae is catalase __ and bacitracin __.

A

-

resistant

61
Q

What are the clinical manifestations of group D strep/enterococcus?

A

URI (rare, but severe in immunocompromised, esp. following GI surgery)

sepsis dt contaminated needle use (rare).

62
Q

How does Staph. aureus cause toxic shock syndrome?

A

The toxin is a superantigen that binds to MHC II protein and T-cell receptors and induces IL-1 and IL-2, causing TSS

63
Q

T/F: S. aureus food poisoning is due to bacterial infiltration of the intestinal wall.

A

F, dt ingestion of preformed enterotoxin

64
Q

What are the clinical manifestations of Strep. viridans?

A

opportunistic infections of heart valves, blood, skin or wounds

Strep. mutans causes dental caries.

65
Q

Identify relevant epidemiology and risk factors associated with Strep. pneumoniae.

A

individuals with depressed cough reflex or damaged mucociliary elevator

pulmonary circulation problems

splenectomy

head trauma

alcoholism

sickle cell anemia

66
Q

What is the morphology of Strep. viridans?

A

cocci

67
Q

How is Strep. pyogenes transmitted?

A

respiratory droplets

direct contact with skin

direct contact with objects.

68
Q

How is Strep. viridans transmitted?

A

usually already present in host

dental work may expose organism to heart valves which, if damaged, may become infected

69
Q

What lab findings are useful to help diagnose group D strep/enterococcus?

A

mostly alpha- or non-hemolytic

resistant to bile salts

70
Q

Name the bacteria that produces a yellow pigment.

A

S. aureus

71
Q

What is the morphology of Staph. aureus?

A

cocci

72
Q

Which are not toxigenic manifestations of Strep. pyogenes: scarlet fever, rheumatic fever, TSS, acute glomerulonephritis.

A

rheumatic fever and acute glomerulonephritis are immune-mediated manifestations

73
Q

How do you differentiate Strep. viridans from Strep. pneumoniae in the lab?

A

both are alpha-hemolytic, but viridans strep is resistant to optochin

74
Q

What is the major reservoir for Strep. pyogenes?

A

human throat and skin

75
Q

Name nine clinical manifestations of Staph. aureus.

A

impetigo

gastroenteritis

infective endocarditis

abscesses and mastitis

TSS

pneumonia

surgical infections

osteomyelitis

necrotizing fasciitis

76
Q

One hour after eating custard at a picnic, the whole family vomits. After 10 hours all are better. Organism?

A

S. aureus (produces preformed enterotoxin)

77
Q

Does Strep. pyogenes gram stain positive or negative?

A

+

78
Q

What is the morphology of Strep. agalactiae?

A

cocci

79
Q

Which of the following agar media is most selective for Staphylococcus aureus?

A

Mannitol salt agar is a selective medium for Staphylococcus aureus.

Mannitol is a carbohydrate that is fermented by S. aureus, leading to acid production and a change in the color of the agar.

80
Q

examples of beta-hemolytic gram + cocci microbes.

A

Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus agalactiae

81
Q

Which 2 staphs are novobiocin sensitive?

A

s. Epidermidis
s. Aureus

82
Q

Food most assoc. w/ s. aureus gastroenteritis?

A

Dairy

83
Q

S. aureus exfoliative toxin cleaves _____

A

desmoglein 1, leading to scalded skin syndrome
Nikolsky sign on infants

84
Q

necrotizing fasciitis is caused by ____ , an endo/exo toxin secreted by s. aureus

A

Panton-Valentine leukocidin is an exotoxin secreted by S. aureus.

85
Q

In the setting of infectious parotitis, serum amylase will be ___while serum lipase will be ___

A

elevated
normal

86
Q

bacterial endocarditis affects which valve first?
Two other signs
Risk factor?

A

Tricuspid valve - tricuspid regurg
Splinter hemorrhages, Osler nodes
IV drug use

87
Q

S. aureus osteomyelitis most commonly affects which bone in adults? Children?

A

Adults - vertebrae
Children - long bones/femur
In diabetics- fist metatarsal

88
Q

what does the mec gene encode for?
How does s. aureus acquire it?

A

PBP-2A is encoded by the mec gene and provides resistance to β-lactam antibiotics.
(Penicillin binding protein)

Acquired via transduction, a form of horizontal gene transfer in which viral bacteriophages transfer bacterial DNA from one bacteria to another.

89
Q

S. epidermidis infections are most commonly associated with

A

Central lines/ foreign body infections

90
Q

Urinalysis in S. saprophyticus UTI will show

A

+ WBCs,
positive leukocyte esterase,
and negative nitrites.

91
Q

OVRPS a

A

Optochin sensitivity
Viridans - resistant
s. Pneumonia - sensitive
Alpha hemolytic

92
Q

B-BRAS

A

Basitracin sensitivity
Group B (agalactiae) - resistant
Group A (pyogenes) - sensitive

93
Q

S. pneumoniae have the ability to cleave which immunoglobulin?

A

IgA, allows it to invade the mucosa

94
Q

S. sanguinis is the most associated with

A

bacterial endocarditis after dental procedures.

95
Q

Toxin assoc. w/ s. pyogenes and function

A

Streptolysin O, highly antigenic exotoxin that degrades cell membranes

96
Q

JONES ->
what disease?
causative agent?

A

S. Pyogenes
RHeumatic fever
Joints - polyarthritis
O (<3) - carditis
Nodules - sub cu
Erythema rash
Sydenham Chorea

Also, ↑ ESR, fever

97
Q

Common findings of scarlet fever

A

sandpaper-like maculopapular rash, strawberry tongue,

98
Q

erysipelas vs. cellulits

A

erysipelas - well demarcated rash on lower limbs (possibly face)
cellulitis - not well demarcated, infection is deep in dermis. Streaking erythema towards lymph nodes

99
Q

Which type of hypersensitivity response is acute rheumatic fever?

A

II

100
Q

Which type of hypersensitivity response is poststreptococcal glomerulonephritis?
Explain

A

III, caused by deposition of antigen-immune complexes in basement membrane of glomerulus.

101
Q

The capsule of s. agalactiae is made of

A

sialic acid polysaccharide capsule

102
Q

Pregnant women are screened for S. agalactiae colonization at which point in gestation?

A

36 w

103
Q

Neonatal meningitis is caused by:
Sings:

A

s. agalactiae
bulging fontanelle, lethargy, hypotonia, poor appetite, and thermoregulatory dysfunction

104
Q

S. gallolyticus (previously named S. bovis)
type of hemolysis
causes
oxygen preference?

A

Gamma hemolysis
Bovis in blood = cancer in colon
facultative anaerobe

105
Q

gallolyticus vs. enterococci

A

gallolyticus is PYR -
enterococci is PYR +
both are gamma-hemolytic

106
Q
A

NPLEX - Micro/Immuno (18 decks)

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