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Microbiology Lecture Slides > Introduction to Diagnostic Microbiology > Flashcards

Introduction to Diagnostic Microbiology Flashcards

1
Q

Some bacteria/fungi are “always” considered pathogens. Two examples of this are

A

M. Tuberculosis and Vibrio Cholerae

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2
Q

How many bacteria must be present to be visible?

A

10^5/mL

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3
Q

hat are three major stains for microscopy?

A

Gram Stain, Ziehl-Neelson or Kinyoun stain, and immunofluorescent antibody stain

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4
Q

The Ziehl-Neelson or Kinyoun stain is used for

A

Myobacteria

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5
Q

A broth culture “back up” in highly enriched medium is required for normally

A

Sterile specimens

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6
Q

What are two rapid bench methods for bacterial identification?

A

Coagulase tubes and catalase test

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7
Q

What are the three advantages of MALDI-TOF for bacterial identification

A

Accuracy, speed, and cost

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8
Q

What are two forms of direct antigen detection?

A

Enzyme Immunoassays (EIAs) and Latex agglutination

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9
Q

What are two examples of EIAs?

A

Rapid strep and rapid influenza

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10
Q

May be used for identification after culture or to directly test specimens

A

Molecular diagnostics

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11
Q

Molecular diagnostics such as nucleic acid amplification tests and DNA sequencing or fingerprinting generally exhibit high

A

Sensitivity and specificity

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12
Q

Has implications for admission decisions, Abx administration, or additional diagnostic testing

A

Respiratory virus panels

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13
Q

Respiratory virus panels have variable numbers/types of targets and can be either

A

On demand or batched

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14
Q

Takes approximately 1-2 hours and can test for 14 target pathogens at once

A

CNS infection panels

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15
Q

Should be interpreted in the context of other laboratory data, i.e. cell count, protein, glucose, and Gram stain

A

CNS infection testing

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16
Q

The main objective of antimicrobial susceptibility testing is to predict the outcome of

A

Prescribed drug

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17
Q

Antimicrobial susceptibility testing can also be used to confirm/refute current

A

Empiric Rx

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18
Q

An infection due to the strain may be appropriately treated with the dosage of anti-microbial agent recommended for that type of infection and species

A

Susceptible (S)

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19
Q

The MIC approaches usually give attainable blood and tissue levels

-response rate may be lower than susceptible isolates

A

Intermediate (I) Susceptibility

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20
Q

Applicable in infection sites where the drug is concentrated (like in urine) or high doses can be used (B-lactams)

A

Intermediate (I) Susceptibility

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21
Q

When strains are not inhibited by usually achievable systemic antimicrobial levels

A

Resistant (R)

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22
Q

In Resistance (R), the MIC falls in the range where specific microbial resistance mechanisms are likely. For example, with

A

B-lactamases

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23
Q

Roughly speaking, is equal to the concentration of antimicrobial at the site of infection

A

Therapeutic Breakpoint or “Breakpoint”

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24
Q

Comparing the MIC to the breakpoint determines

A

Susceptible-intermediate-resistant interpretation

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25
Q

If the MIC is greater than the breakpoint, then the bacteria is

A

Resistant (R)

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26
Q

If the MIC is equal to the breakpoint, then the bacteria is

A

Intermediate (I)

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27
Q

If the MIC is less than the breakpoint, then the bacteria is

A

Susceptible (S)

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28
Q

What is the typical bacteria load in a patient with bacteremia?

A

1 cfu/mL

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29
Q

Most positive blood cultures will show in

A

2 days

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30
Q

If patient has Candida albicans/tropicalis, treat with

A

Fluconazole

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31
Q

If patient has Candida parapsilosis, treat with

A

Azole (or if higher MIC echinocandins)

32
Q

If patient has Candida krusei/glabrata, treat with

A

Echinocandin (Azole resistance)

33
Q

If candida is not detected, then consider withholding

A

Antifungal

34
Q

Most common micro specimen. Received fresh (within 2 hours) or in boric acid

A

Urine cultures

35
Q

The normal flora of the urethra includes which three bacteria?

A

Lactobacillus, streptococci, and staphylococci

36
Q

You want to discard the first part of the urine unless you are testing for

A

GC and chlamydia

37
Q

A high volume of urine is required to detect

A

Myobacteria, cryptococcus, and dimorphic fungi

38
Q

A throat swab only detects

A

GSA

39
Q

You can perform an NP swab/wash, or OC swab/scraping to test for

A

Influenza

40
Q

Not useful for diagnosis of sinusitis

A

NP swabs

41
Q

The most common lower respiratory tract specimens are properly collected

A

Sputum and trach aspirate

42
Q

Assessed for contamination based on presence of epithelial cells/absence of neutrophils

A

Sputum

43
Q

What are the only three bacteria types that contaminated sputum specimens are still ok for?

A

Legionella, nocardia, and myobacterium spp

44
Q

Can be used to test for S. pneumoniae and Legionella

-Should be supplemented with Cx

A

Urine Ag testing

45
Q

Routine Gram stain and Cx, requires how much sterile body fluid per test?

A

1-2 mL

46
Q

However, to perform Gram stain or Cx on myobacterial or fungal analysis, we need

A

Greater than 5 mL each

47
Q

Concentrated prior to microscopy

-most cultures positive in 1-2 days

A

CSF

48
Q

Most untreated patients with bacterial meningitis should have a positive

A

GS (except listeria)

49
Q

Bacterial antigen testing is rarely useful for

A

CSF

50
Q

When testing CSF, what are the tests of choice for Borrelia and Treponema pallidum?

A

Serology or NAATs

51
Q

May be inoculated to blood Cx bottle with additional fluid for Gram stain, NAAT, or Ag testing (in sterile container)

A

Peritoneal/pleural fluid

52
Q

There are no swabs for

A

Peritoneal/pleural fluid

53
Q

Better than a rectal swab for testing gastrointestinal specimens

A

Stool

54
Q

We do not perform a bacterial Cx or parasite exam on patients who have been hospitalized for

A

More than 3 days

55
Q

We test one specimen per day x 3 days for stool for

A

Cx and OP exam

56
Q

What are the three routine bacteria in gastrointestinal specimens?

A

Campylobacter, Salmonella, and Shigella

57
Q

Better than testing WBCs to test for inflammatory response because neutrophils may be degraded

A

Lactoferrin

58
Q

We test for Shiga toxin/SMAC only when there is

A

Bloody stool

59
Q

On a GI specimen, we can test for C. difficile using

A

Antigen or DNA detection

60
Q

Antigen testing is also used on GI specimens to test for

A

H. Pylori

61
Q

With vaginitis, we use direct smears (wet preps) to test for

A

Candidiasis and Trichomoniasis

62
Q

On GU specimens, Gram stain can be used to test for

A

Bacterial vaginosus (GNR > GPR)

63
Q

In GU specimens, for a symptomatic man, GC/chlamydia, and trichomoniasis can be tested using

A

Gram stain

64
Q

In aGU specimen, we test for T. pallidum using

A

Darkfield, DFA, or Serology

65
Q

An acid fast stain (Kinyoun fluorescent) test is used in

A

Myobacteriology

66
Q

In myobacteriology, are rapid and require culture confirmation

A

NAATs

67
Q

What is the incubation period in myobacteriology?

A

6 week incubation

68
Q

There is a long incubation period in

A

Mycology

69
Q

In mycology, for yeasts, what kind of agar do we use?

A

Chromogenic agar (colorimetric species identification)

70
Q

Microscopy is of limited value for

A

Virology

71
Q

Culturing is slow but sensitive

-Shell vial culture improves rates of detection

A

Virology

72
Q

Useful for viral infections where other diagnostic approaches do not exist or are ineffective (i.e. HIV, Hepatitis)

A

Serology

73
Q

The vast majority of testing in virology is now

A

NAAT based

74
Q

Predominantly microscopy based

-However there is antigen detection for common GI parasites

A

Parasitology

75
Q

In parsitology, we use antigen detection for common GI parasites like

A

Giardia

Microbiology Lecture Slides (24 decks)

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