Exam 4 - 29. Introduction to Clinical Microbiology

Question 1

3

What are three lab methods to determine etiology?

Question 2

3

Which lab method to determine etiology is used most often?

Question 3

3

What are the two categories of methods to determine the antimicrobial susceptibility of the causative agent?

Question 4

4

What is of critical importance for analysis of specimens?

Question 5

4

What two things contribute to the quality of the specimen?

Question 6

5

How long does culture usually take?

Question 7

5

Instead of cell culture, what do we mainly use for culturing now?

Question 8

6

What does this describe?

■ Living cells growing in tubes, plates or bottles
■ Used for cultivating viruses & highly fastidious bacteria
■ Observe for cytopathic effects

Question 9

7

Is artificial culture a living or non-living system?

Question 10

7

Artificial culture media can cultivate most ____ and _____.

Question 11

7

What are the two forms of artificial culture media?

Question 12

7

Of the two forms of artificial culture media, which can assess purity and which cannot?

Question 13

8

■Nutritionally fastidious organisms
■ Vitamins, minerals, cofactors ■ Chocolate & blood agars

Question 14

8

What two organisms use enriched media to be identified?

Question 15

9

■ Select for certain organisms, inhibit others
■ Selective agents - dyes, antibiotics, salts

Question 16

9

When is selective media useful?

Question 17

9

What are two examples of selective media?

Question 18

10

■ Make certain organisms “look different” from others (colony appearance)
■ Differential agents - sugars (w/ pH indicator)

Question 19

10

When is differential media useful?

Question 20

10

What is an example of differential media?

Question 21

11

What is selective-differential media excellent for?

Question 22

11

What is an example of selective-differential media?

Question 23

12

What are four agar selection factors?

Question 24

13

What are three incubation considerations? (don’t need to know details, just what are the three?)

Question 25

15

What is beta-hemolysis particular good for identifying?

Question 26

16

What does this describe?

“Multiple species isolated based on colony morphology”

Question 27

16

What does mixed culture often signify contamination with?

Question 28

16

Is mixed culture clinically significant?

Question 29

17

What is the main type of stain we do for microscopic morphology?

Question 30

21

Are capsules usually stained or unstained in a Gram stain?

Question 31

21

What are two organisms that have capsules?

Question 32

21

Are spores usually stained or unstained in Gram stains?

Question 33

21

What are two examples of organisms that have spores?

Question 34

22

What organism is the acid-fast stain used for?

Question 35

22

What organism is the modified acid-fast stain used for?

Question 36

23

breaks down H2O2 into H2O & O2 (bubbles)

Question 37

23

What is the primary mass spectrometry molecular method used?

Question 38

24

Are streptococcus and enterococcus catalase positive or negative?

Question 39

24

Is Staphylococcus catalase positive or negative?

Question 40

27

Sequence-based testing is reserved for organisms not reliably identified by _______. This includes ____, ____, and ____.

Question 41

31

What does this describe?

■ Specific antibody bound to solid phase (membrane)
■ Add antigen solution; wash off unbound material
■ Add specific antibody conjugated to enzyme; wash off unbound material
■ Add substrate - color reaction if antigen present

Question 42

32

What does this describe?

■ Extract organism nucleic acid (DNA or RNA) from specimen

Question 43

32

In molecular amplification, what happens if you extract RNA from the specimen?

Question 44

33

What does this describe?

■ Multiplex PCR panels - detect common causes of “syndromes”; fast, good sensitivity/specificity; ⇧ cost

Question 45

35

Is sequence-based identification dependent on detecting a specific target?

Question 46

36

What does this describe?

■ Indirect method - detects specific antibodies to infectious agent
■ Antibodies present & in high concentration

Question 47

36

In serology…

■ ≥ 4-fold rise in titer = ______ infection
■ < 4-fold rise in titer = ____infection

Question 48

37

Serology is the best indicator of ____ and of _____.

Question 49

38

If an antibody is present in serology, what does it mean?

Question 50

38

What two things MAY a serology test indicate?

Question 51

38

What two things may it mean if there is no antibody present in serology testing?

Question 52

39

What does this describe?

Determines if one or more antibiotics may be effective as treatment for infection

Question 53

40

What are the three overarching principles for when to perform Antimicrobial Susceptibility Testing (AST)?

Question 54

41

Phenotypic AST requires ______.

Question 55

41

■ Generally covers all resistance mechanisms
■ Determine relative susceptibility to relevant antibiotics

Question 56

41

If drug is deemed susceptible is it useful or therapy? What about resistant? What about intermediate?

Question 57

43

What are the two treatment guidelines concerning antimicrobial stewardship?

Question 58

44

What does this describe?

■ Report first line, narrow spectrum, inexpensive antibiotic results
■ Withhold second line, broad spectrum, more expensive antibiotic results;
drugs not on formulary
■ Report 2nd line if resistant to 1st line antibiotics
■ Clinician can always call and request reporting of additional agents; these requests will be honored as long as they are appropriate

Question 59

45

What does this describe?

■ On isolate or directly on specimen
■ Detects the common genetic determinant of resistance to the particular
antibiotic; generally not comprehensive
■ Detect resistance gene by molecular method, e.g., PCR; faster (TAT 1-4 hrs)
but more expensive

Question 60

45

In genotypic AST, if the resistance gene is present, what can you assume? What is the caveat for this?

Question 61

45

In genotypic AST, if the resistance gene is absent, what can you assume? What is the caveat to this?