Antibiotic Resistance

Question 1

What is an antibiotic?

Answer 1

A drug that kills or inhibits the growth of microorganisms.

Question 2

What is antiobiotic resistance?

Answer 2

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

Question 3

What is antibiotic susceptibility?

Answer 3

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

Question 4

What is the Minimal Inhibitory Concentration (MIC)?

Answer 4

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

Question 5

What is the Minimal Bactericidal Concentration (MBC)?

Answer 5

Concentration of an antimicrobial that kills bacteria.

Question 6

What is Breakpoint?

Answer 6

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

Question 7

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

Answer 7

T.

Question 8

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

Answer 8

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

Question 9

How does the E-test determine MIC?

Answer 9

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

Question 10

Can MIC be determined with Kirby-Bauer Disk Diffusion?

Answer 10

No.

Question 11

What 2 methods allow determination of MIC?

Answer 11

1. E-test

2. Agar dilution

Question 12

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

Answer 12

The bacteria being tested will be resistant.

Question 13

What is another more clinically useful definition of breakpoint?

Answer 13

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

Question 14

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

Answer 14

T.

Question 15

A low MIC does not determine what?

Answer 15

Resistance or susceptibility.

Question 16

What is the major reason organisms develop resistance to antibiotics?

Answer 16

The use of antibiotics.

Question 17

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

Answer 17

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

Question 18

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

Answer 18

1. Patient expects antibiotic
2. Diagnostic uncertainty
3. Time pressure

Question 19

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

Answer 19

Resistant bacteria or their genetic determinants are selected for.

Question 20

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

Answer 20

T.

Question 21

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

Answer 21

Hand sanitization.

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

What are the 6 mechanisms of antibiotic resistance?

Answer 24

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

Question 25

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

Answer 25

F: many mechanisms.

Question 26

Genes encoding resistance exist where?

Answer 26

Plasmids or chromosomes.

Question 27

What is the major antibiotic degrading enzyme?

Answer 27

Beta-lactamases.

Question 28

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

Answer 28

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.

Question 29

What are the 3 mechanisms of antibiotic degrading enzymes?

Answer 29

1. Sulfonation 2. Phosphorylation 3. Esterification

Question 30

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

Answer 30

Aminoglycosides.

Question 31

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

Answer 31

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

Question 32

What are extended spectrum beta-lactamases (ESBLs)?

Answer 32

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

Question 33

What 2 organisms are ESBLs most often associated with?

Answer 33

1. E. coli | 2. Klebsiella pneumoniae

Question 34

T or F. ESBLs are usually plasmid mediated.

Answer 34

T.

Question 35

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

Answer 35

1. Aminoglycosides 2. Ciprofloxacin 3. Trimethoprim-sulfamethoxazole

Question 36

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

Answer 36

T.

Question 37

ESBLs result in what?

Answer 37

MDR.

Question 38

What are class A carbapenemases?

Answer 38

Antibiotic degrading enzymes.

Question 39

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

Answer 39

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

Question 40

What is the resistance profile like for class A carbapenemases?

Answer 40

Similar to ESBL but also carbapenem resistant.

Question 41

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

Answer 41

T.

Question 42

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

Answer 42

T.

Question 43

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

Answer 43

T.

Question 44

What organism is known for decreased permeability to antibiotics?

Answer 44

Pseudomonas spp.

Question 45

Can decreased permeability be an innate resistance factor?

Answer 45

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

Question 46

What organism is known for having efflux pumps?

Answer 46

Pseudomonas spp.

Question 47

What are 2 common targets of efflux pumps?

Answer 47

1. Tetracyclines | 2. Macrolides

Question 48

What are the 4 places target alteration occurs?

Answer 48

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

Question 49

DNA gyrase target alteration affects which class of antibiotics?

Answer 49

Fluoroquinolones.

Question 50

What species does DNA gyrase target alteration occur in?

Answer 50

Many gram negatives, S. pneumoniae.

Question 51

What 2 species alter their penicillin-binding proteins?

Answer 51

1. MRSA | 2. Penicillin-resistant S. pneumoniae

Question 52

Gram positive cell wall target alteration affects what antibiotic?

Answer 52

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

Question 53

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

Answer 53

Enterococcus sp.

Question 54

Ribosome target alteration affects which 2 classes of antibiotics?

Answer 54

1. Tetracyclines | 2. Macrolides

Question 55

What species are resistant to macrolides via ribosome target alteration?

Answer 55

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

Question 56

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

Answer 56

Intermediate glycopeptide resistant S. aureus.

Question 57

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

Answer 57

From vancomycin-resistant Enterococcus.

Question 58

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

Answer 58

1. erm(B): modifies erythromycin or azithromycin | 2. mef(A): efflux pump

Question 59

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

Answer 59

Vaccinate children.

Question 60

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

Answer 60

UTIs.

Question 61

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

Answer 61

1. Young healthy women | 2. Elderly

Question 62

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

Answer 62

T.

Question 63

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

Answer 63

T.

Question 64

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

Answer 64

T.

Question 65

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

Answer 65

T.

Question 66

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

Answer 66

T.

Question 67

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

Answer 67

T.

Question 68

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

Answer 68

1. Antibiotics use | 2. Not many new antibiotics are being developed

Question 69

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

Answer 69

T.

Question 70

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

Answer 70

Conjugation.