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Clinical Microbiology 2 > 9. Blood Cultures > Flashcards

9. Blood Cultures Flashcards

1
Q

organisms are always in the bloodstream, as in cases of septic shock, endocarditis, typhoid fever or when vascular hardware such as lines and catheters are infected.

A

Continuous bacteremia

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2
Q

Minimum media setup for blood culture subcultures?

A

BAP /CO2
CHOC /CO2
BRUC /ANO2

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3
Q

Organism? Associated w/ bowel cancer

A

Clostridium septicum

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4
Q

most patients present with a flu-like illness that has lasted more than 2 weeks

A

Sub-acute endocarditis

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5
Q

Organism? Acute endocarditis, line infections, abscesses

A

S. aureus

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6
Q

4 organisms that are frequent blood culture contaminants

A
  • Bacillus
  • Coryne
  • P. acnes
  • CoNS
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7
Q

rapid onset of symptoms, most patients are very ill with fever and malaise. Neurological abnormalities, stroke and subdural hemorrhage are not uncommon.

A

Acute endocarditis

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8
Q

When collecting blood from children, we cannot collect ______ of total body volume

A

> 4%

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9
Q

2 main additives in lysis-centrifugation tubes

A

Saponin - lyses RBCs, WBCs

SPS

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10
Q

HACEK group is usually implicated in..?

A

Sub-acute infective endocarditis

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11
Q

3 primary sites of intravascular bacteremia?

A
  • Endocarditis
  • IV catheters
  • Veins
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12
Q

Includes bacteria and their toxins - always

A

Septicemia

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13
Q

Due to congenital heart valve abnormalities

A

Sub-acute endocarditis

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14
Q

Organisms associated w/ biofilm production on IV catheters

A

S. epidermidis

Other CoNS

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15
Q

This antiseptic cannot be used on infants

A

Chlorhexidine gluconate

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16
Q

Organisms are carried via _________ from the source in extravascular bacteremia

A

lymphatics

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17
Q

Why are heparin, EDTA, and citrate UNACCEPTABLE anticoagulants in blood cultures

A

All toxic to organisms

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18
Q

Purpose of 10% sucrose in blood culture bottles

A

Creates a hypertonic solution to support organisms that are cell wall-deficient

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19
Q

Blood culture system that is not suitable for anaerobic culture

A

Biphasic bottles

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20
Q

Ideal and acceptable contamination rate?

A 
Ideal = < 1%
Acceptable = < 3%
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21
Q

Why can’t you use chlorhexidine gluconate on infants?

A

Damages their skin

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22
Q

Organism? Hospitalized and immunocompromised patients

A

Pseudomonads

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23
Q

Organisms that usually cause bacteremia post-surgery or concurrent UTIs or in immunocompromised patients

A

Enterobacteriacea (mostly E. coli, K. pneumoniae)

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24
Q

Max volume of blood that can be drawn from a child weighing < 36.3 kg?

A

No more than 20mL

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25
Q

2 most common organisms implicated in subacute bacterial endocardiditis? Bacteremia type?

A

Viridans group of strep

  • S. mutans
  • S. sanguis

Intermittent

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26
Q

What does SIRS stand for?

A

Systemic inflammatory response syndrome

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27
Q

Isolation of either of these 2 bacteria may suggest occult abscesses

A
  • S. aureus

- Strep anginosis

28
Q

range from minor disruptions like brushing our teeth, to major manipulations of the vascular system

A

Transient bacteremia

29
Q

Isolation of this bacteria may suggest colon cancer

A

Streptococcus bovis

30
Q

Approx. volume of blood in a blood culture?

31
Q

Purpose of 1.2% gelatin in blood culture bottles?

A

Counteracts SPS (but may be inhibitory to some organisms)

32
Q

Organism? Endocarditis; associated w/ colon cancer

33
Q

Sub-acute infective endocarditis is usually due to the __________ group and also _____

A

HACEK; small gnb

34
Q

What to do if blood culture is NEG at day 5?

A

Blind sub to CHOC; keep plates for 3 days

35
Q

organisms enter the bloodstream from another site of infection, for example from an abscess, deep wound or tumour

A

Intermittent bacteremia

36
Q

Purpose of resins in blood culture bottles

A

Absorbs antibiotics without interfering w/ visual examination of cultures or smears

37
Q

3 specific RE components in the circulatory system

A
  • macrophages (produced in speen)
  • antibodies, complement fixation
  • WBCs (neutrophils and monos ingest bacteria, eosinophils target parasites)
38
Q

Most positive blood cultures will show indication within ________ post-collection

39
Q

Biphasic bottles ere initially developed for this organism

40
Q

What are the 4 types of endocarditis?

A
  • Subacute bacterial endocarditis (SBE)
  • Prosthetic valve endocarditis
  • Acute infective endocarditis
  • Sub-acute infected endocarditis
41
Q

Blood culture system w/ 2 separate chambers in a single containter

A

Biphasic bottles

42
Q

Automated blood culture system that monitors gas pressure in each bottle

43
Q

Purpose of Middlebrook broth?

A

Specialized blood culture formula for AFB

44
Q

Exotoxins are mainly produced by __________ bacteria

A

Gram positive

45
Q

How to proceed if LESS than the recommended volume of blood is collected?

A

Inoculate the AEROBIC bottle first (most isolates are either aerobic or facultative anaerobes + yeast won’t grow anaerobically)

46
Q

Isolation of either of these 5 bacteria may suggest neoplasms

A
  • Campy
  • Clostridium septicum
  • S. bovis
  • Aeromonas
  • Plesiomonas
47
Q

CLSI recommendations for drawing blood with respect to endocarditis?

A
  • 3 cultures over 30 mins
  • If neg at 24 hrs => draw an additional 2 sets on Day 2

Total = 5 sets

48
Q

How is blood culture AST reported?

A

Verbally to physician to give a heads up (no written report)

49
Q

Viridans in blood cultures is most often associated with what disease?

A

Sub-acute endocarditis associated w/ heart valve defects

50
Q

Bacteremia where blood is not the primary focus of infection; organism seeds from abscess

A

Intermittent

51
Q

Blood culture system that is best for pediatrics and why

A

Lysis-centrifugation system

Detects atypical infections (most pediatric infections are atypical)

52
Q

4 symptoms of septicemia

A
  1. Fever and chills
  2. Hyperventilation
  3. Skin lesions (toxins)
  4. Changes to mental state
53
Q

Media used for blood culture AST?

54
Q

Organism? Bacteremia primarily in hospitalized patients

A

Enterococci

55
Q

Which 2 types of endocarditis involve a CONTINUOUS bacteremia pattern

A

The ones that have ‘acute’ in it

  • Acute infective endocarditis
  • Sub-acute infective endocarditis
56
Q

3 ways bacteria can be introduced, causing transient bacteremia

A
  • Infected site
  • Non-sterile body site
  • Subclinical infection
57
Q

Best ratio of blood to culture broth?

A

1:5

But good up to 1:10

58
Q

Primary host defense system that removes bacteria from circulation?

A

Reticuloendothelial system (RE system)

59
Q

3 categories of bacteremia

A
  • Transient
  • Intermittent
  • Continuous
60
Q

Most important variable in detecting bacteremia and fungemia?

A

Volume of blood collected per draw

61
Q

Organism? Mostly SBEs

62
Q

S. aureus is primarily implicated in this endocarditis

A

Acute infective endocarditis

63
Q

Organism? Bacteremia in meninges, blood

A

N. meningitidis

64
Q

Lysis-centrifugation tubes have these 2 additives

A
  • Saponin (lyse RBCs, WBCs)

- SPS

65
Q

Organism associated w/ IV catheters

66
Q

Endotoxins are mainly produced by ________ bacteria

A

Gram negative

67
Q

How often are negative blood culture reports generated?

A

Daily (@24 hrs, 48 hrs)

Clinical Microbiology 2 (14 decks)

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