Ch 15: Diagnosing Infections Flashcards Preview

BIO 246: Microbiology of Human Disease > Ch 15: Diagnosing Infections > Flashcards

Flashcards in Ch 15: Diagnosing Infections Deck (9)
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1
Q

What are the types of testing that can diagnose infections?

A

PHENOTYPIC
- Physical or biochemical observations

GENOTYPIC
- Genetic analysis

IMMUNOLOGIC

  • Pathogen-specific antibodies produced by host
  • Pathogen-specific antigen in host specimen
2
Q

What are some phenotypic methods for diagnosing infections?

A

Microscopic examination
- Gram stain

Macroscopic examination

  • Culture characteristics
  • Selective and differential media
3
Q

How does a biochemical test (eg. multitest) identify the microbe present?

A

Add unknown microbe + substrate

If enzyme present in microbe = Product formed (+ result)

If enzyme absent in microbe = No Product (- result)

4
Q

What are some Genotypic methods for diagnosing infections?

A

Polymerase Chain Reaction

  • exponential amplification
  • can be visually detected using gel electrophoresis

Fluorescent in situ hybridization (FISH)

  • Fluorescent “tagged” DNA probe is used to detect DNA of the pathogen in a specimen
  • “Tag” is visualized by fluorescence microscopy
5
Q

What are the immunologic methods for diagnosing infections?

A

Test for antibodies in patient specimen or test for antigens in patient specimen

immunoassay “quick test”

enzyme-linked immunosorbent assay (ELISA)

agglutination reactions

immunofluorescence and microscopy

6
Q

How do immunoassay quick test work?

A

“Tagged” antibodies are used to detect antigens of the pathogen

“Tag” is involved in color development

7
Q

How do enzyme-linked immunosorbent assay (ELISA)

work?

A

Coat wells with HIV gp120 (antigen)

Add patient blood samples – HIV positive contains antibodies to gp120 (left), HIV negative contains nonspecific antibodies (right)

Wash away unbound antibodies

Add antibody “tagged” with an enzyme that recognizes Fc of bound antibody

Substrate is added that “tag” will convert from clear to yellow

Yellow color indicates presence of anti-HIV antibodies (HIV positive)

8
Q

How do agglutination reactions work?

A

antibodies are used to detect pathogen-specific antigens in a patient sample by “clumping” reaction

9
Q

What is immunofluorescence and microscopy?

A

Pathogens covered w/ antigens

Antibodies tagged w/ fluorescent molecules

Pathogen “tagged” with fluorescent molecules through antigen-antibody binding