Diagnostics

Question 1

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

Answer 1

Presumptive diagnosis and DDX list

Question 2

Diagnostic tests that detect the infectious agent:

Answer 2

Direct: Microscopy/staining, Ab staining

Isolation and identification

Direct detection of Ag or metabolites (toxins)

Molecular techniques detect bacterial DNA

Question 3

Diagnostic tests that detect host immune response

Answer 3

Serology: humoral immunity

Detection of cell-mediated immunity

Question 4

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

Answer 4

before, acute/early

Question 5

Collection of transudates, exudates, pus, and discharges:

Answer 5

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

Question 6

Collection of lavages and washes:

Answer 6

Use buffered solution (saline or LRS)

Question 7

Collection of feces:

Answer 7

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

Question 8

Best method of urine collection:

Answer 8

Cystocentesis

Question 9

During necropsy, when should you collect samples for culture?

Answer 9

Before anything else to prevent contamination.

Question 10

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

Answer 10

Microscopy!

Question 11

Limitations of light microscopy

Answer 11

Low sensitivity (need ^^ organisms)

Less sensitive for blood and CSF

Some bacteria don’t stain (mycoplasma and spirochetes)

Question 12

Limitations of culture

Answer 12

Time consuming

Supplies and expertise ($)

Question 13

Bacteria that require special culture requests

Answer 13

Mycoplasma
Salmonella
Listeria
Mycobacterium
Campylobacter

Question 14

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

Answer 14

Culture (for growth of non fastidious bacteria)

Question 15

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

Answer 15

Selective

Question 16

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

Answer 16

Differential

Question 17

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

Answer 17

TRUE

Question 18

Considerations when interpreting bacterial growth:

Answer 18

Normal microbiota vs pathogens?

Correlation with clinical signs?

Number of colonies (light/heavy)?

Question 19

Outcomes of bacterial growth for testing:

Answer 19

Accept results (got suspected result)

Don’t accept results (why not tho?)

Further testing required.

Question 20

Disadvantage of using PCR to diagnose

Answer 20

Need to already know genomic info to select appropriate primers.

Question 21

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

Answer 21

Antigens

Question 22

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

Answer 22

Chemicals

Question 23

What test can be used to detect LPS in bacteria?

Answer 23

Limulus amoebocyte assay

Question 24

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

Answer 24

Agglutination, ELISA, precipitation tests, Ab titers

Question 25

What is seroconversion?

Answer 25

Development of Ab after exposure to an antigen.

Question 26

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

Answer 26

A four-fold increase in the titers

Question 27

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

Answer 27

False positives

Question 28

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

Answer 28

False negatives

Question 29

The tuberculin skin test detects the ______ immune response.

Answer 29

cellular

Question 30

A false negative tuberculin skin test can be caused by:

Answer 30

Testing in the early stages of the disease.

Question 31

What are the steps in a Gram stain?

Answer 31

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