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Guest Lecturers > Antibiotic Resistance > Flashcards

Antibiotic Resistance Flashcards

1
Q

What is an antibiotic?

A

A drug that kills or inhibits the growth of microorganisms.

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2
Q

What is antiobiotic resistance?

A

Somewhat arbitrary designation that implies that an antimicrobial will not inhibit bacterial growth at clinically achievable concentrations.

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3
Q

What is antibiotic susceptibility?

A

Somewhat arbitrary designation that implies that an antimicrobial will inhibit bacterial growth at clinically achievable concentrations.

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4
Q

What is the Minimal Inhibitory Concentration (MIC)?

A

Lowest concentration of antimicrobial that inhibits growth of bacteria. Commonly used in clinical lab.

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5
Q

What is the Minimal Bactericidal Concentration (MBC)?

A

Concentration of an antimicrobial that kills bacteria.

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6
Q

What is Breakpoint?

A

The MIC that is used to designate between susceptible and resistant. Set by a committee based on clinical evidence.

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7
Q

T or F. Since the 1990s, new antibiotic development has fallen sharply while bacterial resistance continues to increase.

A

T.

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8
Q

What are the advantages of the automated method of determining MIC?

A

Allows for rapid testing of single organisms for multiple antibiotics. Smaller volume needed and higher throughput.

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9
Q

How does the E-test determine MIC?

A

Strip in culture contains varying antibiotic concentration gradient. The point at which growth is observed to be inhibited is the MIC.

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10
Q

Can MIC be determined with Kirby-Bauer Disk Diffusion?

A

No.

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11
Q

What 2 methods allow determination of MIC?

A
  1. E-test

2. Agar dilution

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12
Q

What can be inferred when the MIC is greater than the breakpoint?

A

The bacteria being tested will be resistant.

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13
Q

What is another more clinically useful definition of breakpoint?

A

The concentration that has to be achieved in the body for efficacy.

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14
Q

T or F. MIC must be considered along with breakpoint to determine efficacy in a clinical setting.

A

T.

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15
Q

A low MIC does not determine what?

A

Resistance or susceptibility.

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16
Q

What is the major reason organisms develop resistance to antibiotics?

A

The use of antibiotics.

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17
Q

What are the 3 patient concerns for wanting an antibiotic prescription?

A
  1. Want clear explanation
  2. Green nasal discharge (pt assumes this means bacterial infection)
  3. Need to return to work
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18
Q

What are the 3 physician concerns for writing an antibiotic prescription?

A
  1. Patient expects antibiotic
  2. Diagnostic uncertainty
  3. Time pressure
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19
Q

What happens when colonizing or infecting bacteria are exposed to antibiotics?

A

Resistant bacteria or their genetic determinants are selected for.

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20
Q

T or F. Resistant bacteria can be transmitted between patients.

A

T.

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21
Q

What is the major way to eliminate spread of resistant bacteria?

A

Hand sanitization.

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22
Q

What are the 3 high risk patient populations for the development of resistant bacteria?

A
  1. Immunocompromised
  2. Hospitalized
  3. Invasive devices (especially central venous catheters)
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23
Q

When bacteria are under increasing antibiotic selection pressure, what 3 things occur?

A
  1. Bacteria resistant to a particular drug are selected and replicate
  2. Different antibiotics select different bacteria but can select resistant phenotypes to other drugs as well
  3. This results in multi-drug resistance (MDR) organisms and increases their total number
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24
Q

What are the 6 mechanisms of antibiotic resistance?

A
  1. Decreased permeability
  2. Efflux pumps
  3. Alteration in target molecules
  4. Antibiotic degrading enzymes
  5. Antibiotic resistant genes
  6. Antibiotic altering enzymes
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25
Q

T or F. Many MDR bacteria often only have one mechanism of antibiotic resistance.

A

F: many mechanisms.

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26
Q

Genes encoding resistance exist where?

A

Plasmids or chromosomes.

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27
Q

What is the major antibiotic degrading enzyme?

A

Beta-lactamases.

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28
Q

Why are beta-lactamases more potent in gram negative bacteria?

A

Gram negative contain outer membrane. So when beta-lactamases are released they stay in periplasmic space and thus there is a higher concentration of b-lactamases in gram negative bacteria.

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29
Q

What are the 3 mechanisms of antibiotic degrading enzymes?

A
  1. Sulfonation
  2. Phosphorylation
  3. Esterification
30
Q

What class of antibiotics are antibiotic degrading enzymes especially a problem for?

A

Aminoglycosides.

31
Q

Why are antibiotic degrading enzymes the most efficient mechanism of antiobiotic resistance?

A

There is no sacrifice of normal machinery by the bacteria. The bacteria is gaining a new property, not changing a normal property.

32
Q

What are extended spectrum beta-lactamases (ESBLs)?

A

Beta-lactamases capable of hydrolysing extended spectrum cephalosporins, penicillins, and aztreonam.

33
Q

What 2 organisms are ESBLs most often associated with?

A
  1. E. coli

2. Klebsiella pneumoniae

34
Q

T or F. ESBLs are usually plasmid mediated.

A

T.

35
Q

What 3 drugs’ resistance is often encoded on the same plasmid as ESBLs?

A
  1. Aminoglycosides
  2. Ciprofloxacin
  3. Trimethoprim-sulfamethoxazole
36
Q

T or F. ESBLs have become a significant resistance determinate in acute and long-term care facility enteric pathogens.

A

T.

37
Q

ESBLs result in what?

A

MDR.

38
Q

What are class A carbapenemases?

A

Antibiotic degrading enzymes.

39
Q

Class A carbapenamases are most common in what organism? Where other organisms have them?

A

Klebsiella pneumoniae. E. coli, Enterobacter, Citrobacter, Salmonella, Serratia, Pseudomonas, and Proteus.

40
Q

What is the resistance profile like for class A carbapenemases?

A

Similar to ESBL but also carbapenem resistant.

41
Q

T or F. Class A carbapenemases often have multiple other drug resistance mechanisms.

A

T.

42
Q

T or F. Class A carbapenemases are emerging in long-term care facilities.

A

T.

43
Q

T or F. Decreased permeability affects many antibiotics including carbapenems.

A

T.

44
Q

What organism is known for decreased permeability to antibiotics?

A

Pseudomonas spp.

45
Q

Can decreased permeability be an innate resistance factor?

A

Yes: ex. vancomycin too big to permeate gram negative bacteria.

46
Q

What organism is known for having efflux pumps?

A

Pseudomonas spp.

47
Q

What are 2 common targets of efflux pumps?

A
  1. Tetracyclines

2. Macrolides

48
Q

What are the 4 places target alteration occurs?

A
  1. DNA gyrase
  2. Penicillin-binding proteins
  3. Gram positive cell wall
  4. Ribosomes
49
Q

DNA gyrase target alteration affects which class of antibiotics?

A

Fluoroquinolones.

50
Q

What species does DNA gyrase target alteration occur in?

A

Many gram negatives, S. pneumoniae.

51
Q

What 2 species alter their penicillin-binding proteins?

A
  1. MRSA

2. Penicillin-resistant S. pneumoniae

52
Q

Gram positive cell wall target alteration affects what antibiotic?

A

Vancomycin: normally binds to D-Ala terminal pair…bacteria alter terminal pair to D-Ala D-Lac.

53
Q

What species does gram positive cell wall target alteration occur in?

A

Enterococcus sp.

54
Q

Ribosome target alteration affects which 2 classes of antibiotics?

A
  1. Tetracyclines

2. Macrolides

55
Q

What species are resistant to macrolides via ribosome target alteration?

A

S. pneumoniae, Staphylococcus sp., N. gonorrhoeae, and enteric gram negative rods.

56
Q

Prolonged vancomycin use due to persistent S. aureus infection yields what?

A

Intermediate glycopeptide resistant S. aureus.

57
Q

With high level glycopeptide resistant S. aureus, where is the resistance determinant acquired?

A

From vancomycin-resistant Enterococcus.

58
Q

What are the 2 resistance genes in macrolide-resistant S. pneumoniae and what do they do?

A
  1. erm(B): modifies erythromycin or azithromycin

2. mef(A): efflux pump

59
Q

What is the best way inhibit new resistant strains from being spread within a population?

A

Vaccinate children.

60
Q

Community-acquired resistant E. coli are mostly found in what infection?

A

UTIs.

61
Q

Community-acquired resistant E. coli are most often found in what 2 patient populations?

A
  1. Young healthy women

2. Elderly

62
Q

T or F. Inappropriate and excessive use of antibiotics is a major factor contributing to emerging antibiotic resistance.

A

T.

63
Q

T or F. Determinants of resistance are selected for by antibiotic use.

A

T.

64
Q

T or F. Multiple mechanisms exist for bacteria to become resistant to antibiotics.

A

T.

65
Q

T or F. Antibiotic resistance is a problem in outpatient and inpatient settings and is a factor in a wide variety of infections.

A

T.

66
Q

T or F. Antibiotic resistance continues to emerge as a serious threat to public health.

A

T.

67
Q

T or F. It is our job as physicians to be good stewards of antibiotic treatment to limit resistance.

A

T.

68
Q

What are 2 factors resulting in increased numbers of resistant bacteria?

A
  1. Antibiotics use

2. Not many new antibiotics are being developed

69
Q

T or F. Gram negative bacteria in particular have lots of plasmid mediated resistance mechanisms.

A

T.

70
Q

What is the primary way gram negative bacteria transfer antibiotic resistant genes?

A

Conjugation.

Guest Lecturers (7 decks)

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