Diagnostics Flashcards

1
Q

Following anamnesis, PE, and examination of clinical samples, the clinician must formulate a _____________________.

A

Presumptive diagnosis and DDX list

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2
Q

Diagnostic tests that detect the infectious agent:

A

Direct: Microscopy/staining, Ab staining

Isolation and identification

Direct detection of Ag or metabolites (toxins)

Molecular techniques detect bacterial DNA

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3
Q

Diagnostic tests that detect host immune response

A

Serology: humoral immunity

Detection of cell-mediated immunity

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4
Q

Sample collection should take place _____ antimicrobial therapy and during the ______ stage of the disease.

A

before, acute/early

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5
Q

Collection of transudates, exudates, pus, and discharges:

A

Syringe/sterile container/culturette swab. Use anaerobic transport medium if necessary.

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6
Q

Collection of lavages and washes:

A

Use buffered solution (saline or LRS)

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7
Q

Collection of feces:

A

2-3mg. Repeat sampling for shedding or chronic infections.

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8
Q

Best method of urine collection:

A

Cystocentesis

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9
Q

During necropsy, when should you collect samples for culture?

A

Before anything else to prevent contamination.

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10
Q

What is the most important and cost effective procedure used in identifying number of bacteria, morphology, and host cellular response??

A

Microscopy!

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11
Q

Limitations of light microscopy

A

Low sensitivity (need ^^ organisms)

Less sensitive for blood and CSF

Some bacteria don’t stain (mycoplasma and spirochetes)

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12
Q

Limitations of culture

A

Time consuming

Supplies and expertise ($)

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13
Q

Bacteria that require special culture requests

A
Mycoplasma
Salmonella
Listeria
Mycobacterium
Campylobacter
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14
Q

Nutrient broth, peptone broth, and trypticase soy agar are examples of ______ media.

A

Culture (for growth of non fastidious bacteria)

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15
Q

Phenylethyl Alcohol agar (Gram +), MacConkey agar (Gram -), and Sabourad’s dextrose agar (fungi) are examples of _____ media.

A

Selective

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16
Q

Blood agar and nutrient utilization (lactose fermentation) are what type of media?

A

Differential

17
Q

T/F: a bacterial colony is a visible mass originating from ONE mother cell.

A

TRUE

18
Q

Considerations when interpreting bacterial growth:

A

Normal microbiota vs pathogens?

Correlation with clinical signs?

Number of colonies (light/heavy)?

19
Q

Outcomes of bacterial growth for testing:

A

Accept results (got suspected result)

Don’t accept results (why not tho?)

Further testing required.

20
Q

Disadvantage of using PCR to diagnose

A

Need to already know genomic info to select appropriate primers.

21
Q

ELISA, agglutination, and fluorescent Ab staining are tests that detect:

A

Antigens

22
Q

MALDI-TOF MS, GLC, and analysis of total cell fatty acids are tests that detect:

A

Chemicals

23
Q

What test can be used to detect LPS in bacteria?

A

Limulus amoebocyte assay

24
Q

What tests can be used to detect host humoral immune response?

A

Agglutination, ELISA, precipitation tests, Ab titers

25
Q

What is seroconversion?

A

Development of Ab after exposure to an antigen.

26
Q

When comparing acute phase and convalescent serum titers, what will indicate an infection?

A

A four-fold increase in the titers

27
Q

Prior Ag exposure, vaccination, and cross-reactions can cause ______ _____ on a serum titer.

A

False positives

28
Q

Anergy and immunosuppression can cause _____ _____ on a serum titer.

A

False negatives

29
Q

The tuberculin skin test detects the ______ immune response.

A

cellular

30
Q

A false negative tuberculin skin test can be caused by:

A

Testing in the early stages of the disease.

31
Q

What are the steps in a Gram stain?

A
  1. Crystal Violet
  2. Iodine (mordant)
  3. Alcohol (decolorizer)
  4. Safranin