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Phase 2 Block 1 > Gram Positive Cocci > Flashcards

Gram Positive Cocci Flashcards

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1
Q

There are 5 factors to take into consideration when assessing a pt for infection

A

Epidemiology of pathogen
Patient risk factors
Pre-analytics (factors before a sample is analyzed)
Analytics (how the sample is analyzed)
Post-analytics (how the analysis is reported

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2
Q

Which analytics step has the highest rate of errors?

A

Pre-analytics; analytics and post-analytics are lab controlled while pre- is not

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3
Q

What is the most important pre-analytic factor for getting an accurate result?

A

Volume

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4
Q

What does gram staining help with?

A

Guides workup and tx

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5
Q

What are the 3 types of media used in analytics of bacteria?

A

Enriched
Selective
Differential

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6
Q

What are the 3 types of hemolysis patterns?

A

⍺
β
γ

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7
Q

What colour is the staining associated with ⍺ hemolysis staining pattern?

A

Greening

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8
Q

What colour is the staining associated with β hemolysis staining pattern?

A

Clearing around the colonies

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9
Q

What colour is the staining associated with γ hemolysis staining pattern?

A

No hemolysis

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10
Q

What 3 things are looked at in analytics of a blood agar plate?

A

Hemolysis patterns
Colour of colonies
Shape of colonies

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11
Q

What are the 4 testing methods for determining the type of bacteria?

A

Biochemical testing (manual or commercial MALDI-TOF)
Serology
PCR
Antimicrobial susceptibility testing

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12
Q

What determines the shape of a bacteria?

A

The shape of its cell wall determines if it’s coccus, rod, or spiral

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13
Q

What is the coagulase test?

A

Tests for the coagulase enzyme that bacteria use to form a fibrin capsule around themselves to avoid phagocytosis

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14
Q

Describe what a positive coagulase test looks like

A

Clotted or clumping is seen

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15
Q

Is S. Aureus part of normal flora?

A

Yes; skin and nasal cavity
This is the reason for doing MRSA nose swabs

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16
Q

What is virulence?

A

How pathogenic an organism is and is determined by various factors

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17
Q

What type of host-bacteria relationship does S. Aureus demonstrate? (Flora/colonizer, opportunistic, pathogen)

A

Opportunistic pathogens

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18
Q

This bacteria is a leading cause of bacteremia

A

S. Aureus

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19
Q

Describe the gram stain of S. Aureus

A

Gram (+), Coccoid, clusters of grapes

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20
Q

What media are used for identifying S. Aureus?

A

Blood agar and mannitol salt agar

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21
Q

Why is mannitol salt agar used for S. Aureus?

A

Selective and differential agar
Selective: high salt inhibits most other bacteria
Differential: fermentation of mannitol by S. Aureus —> ↓ pH —> colour change in agar

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22
Q

What is the hemolysis pattern of S. Aureus?

A

Β-hemolytic; white-gold

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23
Q

What biochemical tests are positive for S. Aureus? (Catalase, coagulase slide, coagulase tube)

A

Catalase POS
Coagulase slide POS
Coagulase tube POS

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24
Q

What is the minimum inhibitory concentration?

A

Lowest drug concentration needed to inhibit visible growth of colonies

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25
At least 90% of isolates of this bacteria make penicillinase
S. Aureus
26
This mobile genetic element —> MRSA
mecA
27
How does mecA create MRSA?
mecA is a genetic element that encodes PBP-2A protein that binds penicillins
28
How are antibiotics selected for S. Aureus?
Abx therapy based on infection site, severity of infection, and probability of resistance
29
What 4 groups of antibiotics is MRSA intrinsically resistant to?
β lactam combo drugs Oral cephems Most cephalosporins Carbapenems
30
What antibiotics is MRSA susceptible to?
Ceftaroline/Ceftobiprole (directly binds PBP-2a) TMP-SMX, clindamycin, doxycycline, vanco, linezolid, daptomycin Dapto is last resort
31
Is S. Lugdunensis part of normal flora?
Yes; skin
32
This bacteria causes infections similar to S. Aureus
S. Lugdunensis
33
What are the differences in biochemical testing between S. Aureus and S. Lugdnensis?
S. aureus is positive in catalase and coagulase (tube and slide) S. Lugdenensis is negative on coagulase tube
34
What is S. Lugdnensis susceptible to?
β lactam combo drugs Oral cephems Most cephalosporins Carbapenems MSSA is also susceptible to these
35
When is contamination of sample suspected instead of pathogen?
When 1/4 of bottles in blood culture yield a bacteria
36
This bacteria is responsible for CA-UTIs commonly in 16-35F in late summer
S. Saprophyticus
37
This enzyme allows S. Saprophyticus to invade the bladder wall
Urease
38
What does a positive urease test look like?
Indicator (phenol red) turns from yellow-orange to pink-red
39
That causes the colour change in the urease test?
Urease enzyme will break down urea into ammonia and CO2 Ammonia is alkaline —> indicator turning pink-red in response to alkaline env
40
What is the treatment for S. Saprophyticus?
Nitrofuratoin, TMP-SMX, Cephalexin
41
There are 2 β-hemolytic streptococci
Group A streptococci — S. Pyogenes Group B streptococci — S. Agalactiae
42
Streptococcus in this group show no hemolysis or ⍺-hemolysis
Viridans group strep
43
What are some clinical diseases associated with group A strep?
Acute pharyngitis Scarlet fever (exotoxin producing strains) Acute rheumatic fever Toxic shock syndrome Skin infections (pyoderma, impetigo, cellulitis) Necrotizing fasciitis (polymicrobial; GAS almost always present)
44
Group A strep diagnostics? Gram stain Media Morphology
Gram (+), coccoid pairs/chains Blood agar media to grow Β-hemolytic, white
45
What is the first line therapy for Group A strep?
Penicillin (macrolide if allergic)
46
What inhibits opsonization of group A strep?
M-protein
47
Is Group A part of normal flora?
Yes; skin and throat Like the S. Aureus of strep
48
Is Group B strep part of normal flora?
Yes; GI and urogenital tract
49
This bacteria is found colonizing in 30% of maternal urogenital tracts and has a 50% chance of transfer to the newborn
Group B strep
50
How is transfer of maternal Group B strep to the newborn prevented?
Penicillin (macrolide if allergic) is given 24-48hrs before delivery to clear the GBS Not permanent, GBS will re-establish
51
How is screening for GBS done in pregnancy?
Rectal swab at 36-38 wks, placed into clear broth that turns orange if GBS is present
52
List the bacteria for which AST is usually not done and are treated empirically instead
S. Saprophyticus Group A Strep (S. Pyogenes) Group B Strep (S. Agalactiae)
53
This bacteria is the main cause of meningitis in people >3mo
S. Pneumoniae
54
What are some clinical diseases are associated with S. Pneumoniae?
Meningitis Otitis media Sinusitis Lower reps tract infection Empyema
55
This bacteria is the main cause of community acquired pneumonia
S. Pneumoniae
56
This biochemical test can help determine with confidence that a suspected bacteria is S. Pneumoniae
Bile solubility - positive This means the colony will lyse in a bile salt plate. May leave behind an imprint
57
This bacteria has different breakpoints in MIC for dosing
S. Pneumoniae
58
This bacteria is less virulent than S. Pneumoniae and can cause deep tissue abscesses. It is commonly seen with anaerobic bacteria
S. Anginosus
59
What antibiotics are used for S. Anginosus?
Penicillin or Ceftriaxone
60
What clinical diseases are associated with e. Faecium and e. Faecalis?
Bacteremia Endocarditis UTIs
61
Enterococcus spp. have a lot of intrinsic resistances, which include:
Most cephalosporins Β-lactams Aminoglycosides Clindamycin Ertapenem Septra
62
95% of E. Faecalis is susceptible to this drug but <5% of e. Faecium are susceptible
Ampicillin
63
What are the therapy options for e. Faecalis and e. faecium?
Synergistic β-lactams + aminoglycosides Vanco Cipro Fosfomycin Nitrofurantoin Daptomycin Linezolid
64
What is the most common enterococci in clinical infections?
e. Faecalis
65
Which enterococci is commonly associated with VRE?
e. Faecium

Phase 2 Block 1 (19 decks)

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