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Clinical Micro 2 Spring 2023 > Exam 2 Review > Flashcards

Exam 2 Review Flashcards

1
Q

How does the BCG vaccine work?

A

Stimluates the cell mediate response. It can be live, or attentuated from M. bovis.

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2
Q

What is used to decontaminate the sputum specimen?

A

To decontaminate the specimen with NaOH

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3
Q

What is used to liquefy the sputum specimen?

A

NALC

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4
Q

What is used in a sputum specimen to eliminate pseudomonas and/or proteus?

A

Zephiran - Trisodium and oxalic acid

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5
Q

A mycobacterium is found to produce pigment in light and was collected from water. What runyon group does it belong to?

A

Runyon Group I

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6
Q

A mycobacterium colony produces pigment in dark or light. What runyon group does it belong to?

A

Runyon Group II

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7
Q

What runyon group does not produce pigment in light or dark conditions?

A

Runyon group III

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8
Q

What class of antibiotic is structurally similar to acyl-D-alanyl-D-alanine?

A

Beta Lactam; It targets cell wall synthesis by binding to PBP

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9
Q

Antibiotics have cillin, penem, and ceph in their names. What class do they belong to?

A

Beta Lactams

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10
Q

What antibiotic requires an anaerobic environment in order for it to be effective?

A

Metronidazole (anti- nucleic acid synthesis)

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11
Q

What specific antibiotic can cause aplastic anemia?

A

Chloramphenicol

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12
Q

What antibiotic class inhibits the enzyme at the first step of cell wall synthesis?

A

Fosfomycin

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13
Q

What class of antibiotics act as a detergent by interacting with the phospholipids of the membrane?

A

Polymyxin. There is severe renal toxicity as a side effect.

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14
Q

What antibiotic is able to insert a hydrophobic tail into the membrane causing leakage and eventually bacteria death?

A

Lipopeptides

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15
Q

Lipopeptides may be effective against bacteria however they should not be used in ____?

A

Respiratory infection because lung surfactant inactivates it.

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16
Q

When can macrolides / ketolides become bactericidal?

A

If bacteria concentration is low and antibiotic concentration is high.

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17
Q

Deleted

A

Deleted

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18
Q

Prescribing clindamycin increases the patient’s risk for…?

A

C diff infection

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19
Q

Chloramphenicol is effective against what kind of bacteria?

A

Gram negative

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20
Q

How does chloramphenicol kill bacteria?

A

Inhibits peptidyl transferase (protein synthesis).

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21
Q

Oxazolidinones target…?

A

23S ribosomal RNA of the 50S subunit (protein synthesis). This prevents the formation of the function 70S initiation complex preventing replication and translation

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22
Q

Dalfopristin targets…?

A

Ribosomal 50S subunit causing a change in conformation (antiprotein synthesis)

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23
Q

Tetracycline and glycylglycines work against bacteria by targeting

A

The 30S subunit. Tetracycline binds irreversibly and glycylglycine binds reversibly to the 30S subunit.

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24
Q

Quinolones kill bacteria by targeting…?

A

DNA Gyrase and topoisomerase

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25
Q

What is a side effect of quinolones?

A

Tendon rupture and tendonitis

26
Q

What environment does metronidazole require in order to work?

A

anaerobic atmosphere

27
Q

Rifampin targets

A

RNA polymerase and works best on gram positive

28
Q

Bacteria colonies growing on a plate that look like bread crumbs. What could it be?

A

Fusobacterium nucleatum

29
Q

Bacteria colonies growing on a plate that are black pigmented colonies or black halo. What could it be?

A

Prevotella melaninogenica or porphyromonas spp.

30
Q

Bacteria colonies growing on a plate made pits in the plate. What could it be?

A

Bacteroides ureolyticus

31
Q

Bacteria colonies growing on the plate. You take a UV light and they fluoresce red. What could they be?

A

Porphyromonas gingivalis

32
Q

Ground glass colonies growing on a plate and fluoresce yellow green. What could they be?

A

Clostridium difficle

33
Q

You look at a plate and they look like molar tooth and have sulfur granules. What could they be?

A

Actinomyces israelii

34
Q

What bacteria grows on skin naturally and produce propionic acid?

A

Propionibacterium acnes

35
Q

A blood agar plate is examined with two zones of hemolysis. The inner zone is clear and the outer zone is partial hemolysis. What could the bacteria be?

A

Clostridium perfringens

36
Q

A bacteria growing on a plate looks like small gray-white colones and smells sweet. The biochemical tests are
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?

A

Bacteroides fragilis

37
Q

Pinpoint gray - white colones with black pigmented center is growing on the plate. The biochemical tests done are:
1. Indole +ve
2. Bile esculin -ve
3. Glucose +ve
What could this bacteria be?

A

Fusobacterium nucleatum

38
Q

Bacteria colonies that look small, gray-black colonies with “halo”.
Biochemical tests are
1. Indole +ve
2. Bile esculin +ve
3. Glucose +ve
What could this bacteria be?

A

Prevotella, the halo is due to melanin pigment. (There is one other bacteria that shows a halo).

39
Q

Bacteria colonies that are small, gray-white colonies and smell like ammonia. The biochemical tests results are:
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?

A

Bacteroides ureolyticus

40
Q

Bacteria colonies that look like small, gray - black colonies with a halo. The biochemical results are
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?

A

Porphyromonas spp., Halo is made from porphyrin pigment

41
Q

What is presumptive identification?

A

Based on phenotypic characteristics such as colonial morphology, Gram stain, and biochemical reactions. Tests used to provide preliminary identification of the organism and guide further confirmatory testing. (Ex. -> Bile esculin agar for detection of Enterococcus spp. and Bacteroides fragilis group)

42
Q

What is definitive identification?

A

Based on specific tests that confirm identity of organism. (Ex. -> PCR testing or ELISA for detection of specific antigens or antibodies). Important for determining antimicrobial susceptibility and epidemiological studies.

43
Q

Describe the gram stain characteristics of bacteroides include shape and pattern.

A

Gram -ve bacilli with tapered ends, possible bipolar staining, “school of fish”, “jigsaw puzzle” due to clumping

44
Q

Describe the gram stain characteristics of fusobacterium include shape and pattern.

A

Gram -ve bacilli with pointed ends and often exhibiting “spindle” or “cigar” shape. May also appear as chains or filaments.

45
Q

Describe the gram stain characteristics of Propionibacterium include shape and pattern.

A

Gram +ve bacilli that may be pleomorphic -> coccobacilli to filaments. Can exhibit branching and club-shaped morphology.

46
Q

Describe the gram stain characteristics of actinomyces include shape and pattern.

A

Gram +ve bacilli often branching and filamentous, resembling hyphae. Can appear as clubs or rods with beaded or clubbed ends.

47
Q

Describe the gram stain characteristics of clostridium include shape and pattern.

A

Gram +ve bacilli usually large and rectangular, with square ends. May appear as long rods or filaments with swollen or spindle-shaped ends.

48
Q

What is clavulanic acid used for in?

A

Extended-spectrum beta - lactamases are inhibited by clavulanic acid; therefore, this property can be used as a confirmatory test in the identification process.

49
Q

What is the purpose of Mcfarland standard?

A

(i.e., 1.5 3 108 CFU/mL) usually serve as the
starting point for dilutions ultimately achieving the required
final standard bacterial concentration of 5 3 105 CFU/mL
in each microtiter well.

50
Q

Define intrinsic resistance

A

Antimicrobial resistance resulting from normal genetic, structural, or physiologic state of a microorganism

51
Q

Why is there a natural resistance in anaerobic bacteria versus aminoglycosides?

A

Lack of oxidative metabolism
to drive uptake of aminoglycosides

52
Q

Why is there a natural resistance in gram-positive bacteria versus aztreonam (beta lactam)?

A

Lack of penicillin-binding protein (PBP) targets that bind
this beta-lactam antibiotic

53
Q

Why is there a natural resistance between gram-negative bacteria versus vancomycin?

A

Lack of uptake resulting from
inability of vancomycin to
penetrate outer membrane

54
Q

Why is there a natural resistance between pseudomonas aeruginosa versus sulfonamides, trimethoprim, tetracycline, or chloramphenicol?

A

Lack of uptake resulting in
ineffective intracellular
concentrations of these
antimicrobials

55
Q

Why is there a natural resistance between Klebsiella versus ampicillin targets?

A

Production of enzymes (betalactamases) that destroy
ampicillin before it reaches
its PBP target

56
Q

Why is there a natural resistance between aerobic bacteria versus metronidazole?

A

Inability to anaerobically reduce drug to its active form.

57
Q

Why is there a natural resistance between enterococci versus aminoglycosides?

A

Lack of sufficient oxidative metabolism to drive uptake of aminoglycosides

58
Q

Why is there a natural resistance between enterococci versus all cephalosporins?

A

Lack of PBPs that effectively
bind and are inhibited by
these beta-lactam agents

59
Q

Why is there a natural resistance between lactobacilli and leuconostoc spp. versus vancomycin?

A

Lack of appropriate cell wall
precursor target to bind
vancomycin and inhibit cell
wall synthesis

60
Q

Why is there a natural resistance between stenotrophomonas maltophilia versus imipenem?

A

Production of enzymes (betalactamases) that destroy
imipenem before it reaches PBP targets

61
Q

List methods for a bacteria to combat antibiotics.

A
  1. Enzymatic degradation or modification of the antimicrobial agent
  2. Decreased uptake or accumulation of the antimicrobial agent
  3. Altered antimicrobial target
  4. Circumvention of the consequences of antimicrobial action
  5. Uncoupling of antimicrobial agent–target interactions and subsequent effects on bacterial metabolism
  6. Any combination of mechanisms 1 through 5

Clinical Micro 2 Spring 2023 (17 decks)

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