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MHD 1 > L21 The Role of Microscopy in the Diagnosis of Infectious Disease > Flashcards

L21 The Role of Microscopy in the Diagnosis of Infectious Disease Flashcards

1
Q

Different ___ are used to cultivate bacteria. Growth depends on specimen type and/or the clinical disease.

A

Agars

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2
Q

What are the 4 major types of microscopy?

A
  1. Bright field (light)
  2. Dark field
  3. Fluorescence
  4. Electron microscopy
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3
Q

What microbes can be seen using light microscopy?

A
  1. Bacteria
  2. Fungi
  3. Parasites
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4
Q

What microbes can be seen using dark field microscopy?

A
  1. Spirochetes
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5
Q

What microbes can be seen using fluorescent microscopy?

A
  1. Bacteria
  2. Fungi
  3. Parasites
  4. Viruses
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6
Q

What microbes can be seen using electron microscopy?

A
  1. Viruses

2. Microsporidia

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7
Q

What color does a Gram positive bacteria stain? Gram negative?

A

Gram positive: purple

Gram negative: pink

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8
Q

In addition to bacteria, a Gram stain can help observe the presence of ___.

A

Inflammatory cells

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9
Q

Describe the steps of a Gram stain procedure.

A
  1. Plate the cells on a slide
  2. Primary stain - crystal violet
  3. Apply iodine to set the dye
  4. Decolorizer -alcohol/acetone (positive remains purple, negative becomes colorless)
  5. Counterstain - safranin (positive remains purple, negative becomes pink/red)
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10
Q

Why are Gram positive bacteria resistant to decolorization by alcohol/acetone?

A

They have a thick wall of peptidoglycan

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11
Q

What are the 4 clinical utilities of Gram stain?

A
  1. Direct examination of clinical material to make an initial diagnosis
  2. Determine the quality of the specimen
  3. Suggest an unusual organism or provide early presumptive bacterial identification
  4. Verify the clinical relevance of the culture
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12
Q

Streptococcus pneumoniae is a Gram ___ (+/-) ___ (shape).

A

Positive (purple); diplococci

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13
Q

Neisseria gonococcus is a Gram (+/-) ___ (shape).

A

Negative (pink);

diplococci

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14
Q

Neisseria meningitidis is a Gram (+/-) ___ (shape).

A

Negative (pink); cocci

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15
Q

What is a cryptococcus and how does it stain?

A

Fungi; purple-ish with a clear area (capsule) surrounding it

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16
Q

What type of bacteria is seen in normal vaginal secretions? Describe its stain and shape.

A

Lactobacilli; seen inside squamous cells; Gram positive (purple); rod

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17
Q

How will bacterial vaginosis differ from normal vaginal secretions on the molecular level?

A

The Gram positive bacilli are less present; there are multiple shapes of bacteria and more bacteria

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18
Q

How can you identify a respiratory specimen as poor quality?

A

Presence of lots of squamous cells

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19
Q

How can you identify a respiratory specimen as good quality?

A

Presence of ciliated columnar cells and/or neutrophils

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20
Q

Actinomyces are ___ (shape) and stain ___ on a Gram stain.

A

Filamentous; Gram positive (purple)

21
Q

Campylobacter jejuni are Gram ___ (+/-) ___ (shape). What do they look like?

A

Negative (pink); rods; seagulls

22
Q

Nocardia are Gram ___ (+/-) ___ (shape). What is unique about the appearance?

A

Positive (purple); filamentous with beading

23
Q

Clostridium tetani are Gram ___ (+/-) ___ (shape). What do they look like?

A

Positive (purple); rod with round terminal spores; drumsticks

24
Q

When do we do a blood culture?

A

When we are concerned that there is bacteria in the bloodstream (bacteremia)

25
Q

How do we know if a bacterium that is normally found in the body is causing an infection or not?

A

Presence of inflammatory cells

26
Q

What are acid fast stains used for?

A

To stain bacteria with cell walls containing long chain fatty acids

27
Q

What qualifies as an acid fast bacilli?

A

Cells that resist decolorization after heat or detergent is used to drive the stain into the cell

28
Q

What are the 4 types of microbes stained by acid fast?

A
  1. Mycobacteria
  2. Nocardia
  3. Cyrptosporidia
  4. Cyclospora
29
Q

What are the 2 methods of acid fast staining and how are they different?

A
  1. Ziehl-Neelsen (uses heat)

2. Kinyoun (does not use heat)

30
Q

What are the steps of the acid fast procedure?

A
  1. Plate cells on a slide
  2. Primary stain (carbalfuchsin red)
  3. Decolorizer (HCl, alcohol)
  4. Counterstain (methylene blue) –> acid fast stay red
31
Q

What are the two types of silver stains?

A
  1. Warthin-Starry

2. Steiner

32
Q

What type of tissue is needed for a silver stain?

A

Formalin fixed tissue

33
Q

What are two examples of microbes that can be seen with a silver stain?

A
  1. Spirochetes like Treponema pallidum (syphillis)

2. Bartonella henselae (cat scratch disease)

34
Q

What are 4 special stains used for fungi?

A
  1. Lactophenol cotton blue
  2. Gomori methenamine silver (GMS)
  3. Periodic acid-Schiff (PAS)
  4. Mucicarmine (mucin)
35
Q

What can be seen using GMS?

A
  1. Yeast cells and hyphae

2. Pneumocystis jiroveci

36
Q

What can be seen using PAS?

A
  1. Yeast cells and hyphae
37
Q

What can be seen using mucicarmine?

A
  1. Cryptococcus capsule (the only thing that can be seen with this stain)
38
Q

GMS stains fungi ___ (color).

A

Black

39
Q

What is characteristic of aspergillus?

A

Hyphae with 45 degree angle branching and septae

40
Q

PAS stains fungi ___ (color).

A

Pink

41
Q

Mucin stain stains cryptococcus capsules ___ (color).

A

Very pink

42
Q

What are the 4 types of stains for parasites?

A
  1. Wright Giemsa
  2. Wet mounts
  3. Trichrome
  4. Modified acid fast
43
Q

Which parasite stain is used to examine a peripheral blood smear?

A

Wright Giemsa

44
Q

What 3 microbes does Wright Giemsa help detect?

A
  1. Leishmania
  2. Trypanosomas
  3. Malaria
45
Q

True or false - parasites are cultured in order to be studied.

A

False - they are not cultured; they are looked at under a microscope.

46
Q

How does a fluorescence stain work?

A

Fluorophores or fluorochromes absorb energy from nonvisible UV and short visible wavelengths, become excited, and emit the energy in the form of longer visible wavelengths

47
Q

What are the three types of fluorescent microscopy and what microbes do they identify?

A
  1. Auramine-rhodamine (mycobacteria)
  2. Calcofluor white stain (fungi)
  3. Flurescin conjugated antibodies (viruses, bordetella, legionella, pneumocystis)
48
Q

___ in the cell wall of fungi will take up calcofluor.

A

Chitin

MHD 1 (58 decks)

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