Exam 4 - 29. Introduction to Clinical Microbiology Flashcards
3
What are three lab methods to determine etiology?
3
Which lab method to determine etiology is used most often?
3
What are the two categories of methods to determine the antimicrobial susceptibility of the causative agent?
4
What is of critical importance for analysis of specimens?
4
What two things contribute to the quality of the specimen?
5
How long does culture usually take?
5
Instead of cell culture, what do we mainly use for culturing now?
6
What does this describe?
■ Living cells growing in tubes, plates or bottles
■ Used for cultivating viruses & highly fastidious bacteria
■ Observe for cytopathic effects
7
Is artificial culture a living or non-living system?
7
Artificial culture media can cultivate most ____ and _____.
7
What are the two forms of artificial culture media?
7
Of the two forms of artificial culture media, which can assess purity and which cannot?
8
■Nutritionally fastidious organisms
■ Vitamins, minerals, cofactors ■ Chocolate & blood agars
8
What two organisms use enriched media to be identified?
9
■ Select for certain organisms, inhibit others
■ Selective agents - dyes, antibiotics, salts
9
When is selective media useful?
9
What are two examples of selective media?
10
■ Make certain organisms “look different” from others (colony appearance)
■ Differential agents - sugars (w/ pH indicator)
10
When is differential media useful?
10
What is an example of differential media?
11
What is selective-differential media excellent for?
11
What is an example of selective-differential media?
12
What are four agar selection factors?
13
What are three incubation considerations? (don’t need to know details, just what are the three?)
15
What is beta-hemolysis particular good for identifying?
16
What does this describe?
“Multiple species isolated based on colony morphology”
16
What does mixed culture often signify contamination with?
16
Is mixed culture clinically significant?
17
What is the main type of stain we do for microscopic morphology?
21
Are capsules usually stained or unstained in a Gram stain?
21
What are two organisms that have capsules?
21
Are spores usually stained or unstained in Gram stains?
21
What are two examples of organisms that have spores?
22
What organism is the acid-fast stain used for?
22
What organism is the modified acid-fast stain used for?
23
breaks down H2O2 into H2O & O2 (bubbles)
23
What is the primary mass spectrometry molecular method used?
24
Are streptococcus and enterococcus catalase positive or negative?
24
Is Staphylococcus catalase positive or negative?
27
Sequence-based testing is reserved for organisms not reliably identified by _______. This includes ____, ____, and ____.
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
32
What does this describe?
■ Extract organism nucleic acid (DNA or RNA) from specimen
32
In molecular amplification, what happens if you extract RNA from the specimen?
33
What does this describe?
■ Multiplex PCR panels - detect common causes of “syndromes”; fast, good sensitivity/specificity; ⇧ cost
35
Is sequence-based identification dependent on detecting a specific target?
36
What does this describe?
■ Indirect method - detects specific antibodies to infectious agent
■ Antibodies present & in high concentration
36
In serology…
■ ≥ 4-fold rise in titer = ______ infection
■ < 4-fold rise in titer = ____infection
37
Serology is the best indicator of ____ and of _____.
38
If an antibody is present in serology, what does it mean?
38
What two things MAY a serology test indicate?
38
What two things may it mean if there is no antibody present in serology testing?
39
What does this describe?
Determines if one or more antibiotics may be effective as treatment for infection
40
What are the three overarching principles for when to perform Antimicrobial Susceptibility Testing (AST)?
41
Phenotypic AST requires ______.
41
■ Generally covers all resistance mechanisms
■ Determine relative susceptibility to relevant antibiotics
41
If drug is deemed susceptible is it useful or therapy? What about resistant? What about intermediate?
43
What are the two treatment guidelines concerning antimicrobial stewardship?
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
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
45
In genotypic AST, if the resistance gene is present, what can you assume? What is the caveat for this?
45
In genotypic AST, if the resistance gene is absent, what can you assume? What is the caveat to this?
