Bacterial Identification Flashcards

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1
Q

2 reasons culture is better for bacterial diagnostics than PCR

A
  1. Cost (urine culture $1 vs $15)

2. Sensitivity (culture better than PCR - might not even pick up the bacteria)

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2
Q

MALDI-TOF

A

Matrix assisted laser desorption ionization - time of flight

Move to proteomics and using a mass spec

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3
Q

What are protein biomarkers?

A

Highly expressed proteins responsible for housekeeping functions
Ex: ribosomal (16S) and transcription/translation proteins
These are what are detected in MALDI-TOF

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4
Q

Why is MALDI-TOF better than Vitek?

A

Cheaper**
Faster
Better

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5
Q

Bacteremia

A

The presence of bacteria in the bloodstream

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6
Q

2 mechanisms that bacteremia occurs

A
  1. Drainage from the primary focus of infection via the lymphatic system to the vascular system (ex: abscess)
  2. Direct entry from needles, contaminated IV devices, or graft material or trauma
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7
Q

Transient bacteremia

A

Minutes to hours
Often occurs following manipulation of infected tissues or instrumentation of contaminated mucosal surfaces (ex: brushing teeth)
Onset of acute bacterial infections such a pneumonia, meningitis and septic arthritis

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8
Q

Intermittent bacteremia

A

Most commonly occurs with un-drained abscesses

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9
Q

Continuous bacteremia

A

Usually reflects an endovascular infection such as endocarditis or an infected aneurysm

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10
Q

What are some of the most common primary foci

A

IV devices
Respiratory tract
Urinary tract
Intra-abdominal infections

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11
Q

What 3 bacteria are the most common causes of bacteremia

A

S. aureus and E. coli the most

Coagulase negative Staph is a close third

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12
Q

What are some poor prognosis findings for bacteremia

A
Advanced age
Nosocomial bacteria (more resistant usually)
Enterococcal, gram -'ve, or fungal etiology (harder to treat)
Underlying cirrhosis or malignancy
Primary focus in the resp tract or skin
Surgical wound of abscess
Septic shock
Lack of a febrile response to sepsis
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13
Q

Nosocomial infections

A

Hospital acquired infections

Usually more resistant to drugs

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14
Q

Why do you need to dilute the blood in broth?

A

Diluting greater than 1:5 increases microbial recovery, probably by diluting antimicrobial agents and natural inhibitory factors in the blood

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15
Q

Whats the most common anticoagulant in blood?

A

SPS

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16
Q

Automated blood culture systems

A

24 hour continuous monitoring
When bacteria grow they make CO2 - will change the colour of the membrane and the detector sees that (fluorescence)
Door lights up and sends an alarm

17
Q
How are
1. SBA
2. CHOC
3. BHI
4. MAC
incubated?
A
  1. Aerobically
  2. With 5% CO2
  3. Anaerobically
  4. For gram negatives
18
Q

What is the most common anaerobes you’re going to grow?

A

Bacteriodes

19
Q

What 3 bacteria do not usually represent true bacteremia?

A

Corynebacterium spp
Bacillus spp
Propionibacterium acnes