ID I

Question 1

Gram positive

Answer 1

thick cell wall, dark purple or bluish from crystal violet stain

Question 2

Staphylococci (gram-positive organisms occurring in cluster) can be differentiated with a coagulase (enzyme) test. Which is coagulase positive?

Answer 2

Staphylococcus aureus

Question 3

Gram negative

Answer 3

thin cell wall, pick or reddish from the safranin counterstain

Question 4

What is minimum inhibitory concentration (MIC)?

Answer 4

minimum concentration of each antibiotic that inhibits bacterial growth

REMEMBER: MICs are specific to each antibiotic & organism -> cannot be compared among different antibiotics

Question 5

example of synergism

Answer 5

Aminoglycosides & beta-lactams can be used together synergistically to treat certain invasive gram-positive infections (e.g., infective endocarditis

Question 6

COMMON RESISTANT PATHOGENS

Answer 6

Remember: Kill Each And Every Strong Pathogen

Klebsiella pneumoniae (ESBL, CRE)
Escherichia coli (ESBL, CRE)
Acinetobacter baumannii
Enterococcus faecalis, Enterococcus faecium (VRE)
Staphylococcus aureus (MRSA)
Pseudomonas aeruginosa

Question 7

Risk of C. diff is highest with…

Answer 7

broad-spectrum penicillins and cephalosporins, quinolones, carbapenems, & clindamycin (which has a BBW)

Question 8

Generally, cell wall & cell membrane inhibitors, DNA/RNA inhibitors, and aminoglycosides are __________ (kill bacteria or inhibit bacterial growth?).

Answer 8

bactericidal (kill bacteria)

Question 9

Generally, most protein & folic acid synthesis inhibitors are __________.

Answer 9

bacteriostatic (inhibit growth)

Question 10

Folic acid synthesis inhibitors

Answer 10

• Sulfonamides
• Trimethoprim*
• Dapsone

*often combined with sulfamethoxazole to overcome resistance

Question 11

Protein synthesis inhibitors

Answer 11

• Aminoglycosides
• Macrolides
• Tetracyclines
• Clindamycin
• Linezolid, tedizolid
• Quinupristin/dalfopristin

Question 12

DNA/RNA inhibitors

Answer 12

• Quinolones (DNA gyrase, topoisomerase IV)
• Metronidazole, tinidazole
• Rifampin

Question 13

Cell membrane inhibitors

Answer 13

• Polymyxins
• Daptomycin
• Telavancin
• Oritavancin

Question 14

Protein synthesis inhibitors

Answer 14

• Aminoglycosides
• Macrolides
• Tetracyclines
• Clindamycin
• Linezolid, tedizolid
• Quinupristin/dalfopristin

Question 15

Cell wall inhibitors

Answer 15

• Beta-lactams (penicillins, cephalosporins, carbapenems)
• Monobactams (aztreonam)
• Vancomycin, dalbavancin, telavancin, oritavancin

Question 16

Hydrophilic agents

Answer 16

• Beta-lactams
• Aminoglycosides
• Vancomycin
• Daptomycin
• Polymyxins

Question 17

Features of hydrophilic agents

Answer 17

1) Small volume of distribution -> less tissue penetration
2) Mostly renally eliminated -> drug accumulation & side effects (e.g., nephrotoxicity) can occur if not dose adjusted
3) Low intracellular concentrations -> not active against atypical (intracellular pathogens)
4) Poor-moderate bioavailability -> IV:PO ratio not 1:1

Question 18

Lipophilic agents

Answer 18

• Quinolones
• Macrolides
• Rifampin
• Linezolid
• Tetracyclines

Question 19

Features of lipophilic agents

Answer 19

1) Large Vd -> better tissue penetration
2) Mostly hepatically metabolized -> potential for hepatotoxicity & DDIs
3) Achieve intracellular concentrations -> active against atypical (intracellular) pathogens
4) Excellent bioavailability -> IV:PO ratio often 1:1

Question 20

Drugs with concentration-dependent killing can be dosed ______ frequently and in _______ doses. These antibiotics include…

Answer 20

Drugs with concentration-dependent killing can be dosed less frequently and in higher doses. These antibiotics include:
- aminoglycosides
- quinolones
- daptomycin

Question 21

Drugs with time-dependent killing can be dosed ______ frequently. These antibiotics include…

Answer 21

Drugs with time-dependent killing can be dosed more frequently or each dose can be administered for a longer duration to maximize the time above MIC.
- Examples include extending the infusion time of beta-lactams or administering drug as continuous infusion

These antibiotics include…
- beta-lactams (penicillins, cephalosporins, carbapenem)

Question 22

AUC:MIC (exposure-dependent) drugs

Answer 22

Vancomycin, macrolides, tetracyclines, polymyxins

Question 23

MOA of penicillins

Answer 23

inhibit bacterial cell wall synthesis by binding to PBPs -> prevent final step of peptidoglycan synthesis in bacterial cell walls

Question 24

BOXED WARNING of penicillin G benzathine (Bicillin L-A)

Answer 24

NOT for IV use -> can cause cardiorespiratory arrest & death

Question 25

Severe renal impairment (CrCl <30) -> do not use…

Answer 25

extended-release forms of amoxicillin & amoxicillin/clavulanate (Augmentin XR), or the 875 mg strength of Augmentin

Question 26

side effects of penicillins

Answer 26

• Seizures (with accumulation) when not correctly dose adjusted in renal dysfunction
• GI upset, diarrhea
• Rash (including SJS/TEN/allergic rxns/anaphylaxis
• Hemolytic anemia (identified with positive Coombs test)
• Renal failure
• Myelosuppression with prolonged use
• increased LFTs

Question 27

Which penicillins do NOT require renal dose adjustments?

Answer 27

Antistaphylococcal penicillins (dicloxacillin, naficillin, oxacillin)

Question 28

What is special to know about naficillin specifically?

Answer 28

Naficillin is a vesicant -> administration through central line preferred. If extravasation occurs, use cold packs & hyaluronidase injections

Question 29

What medication can increase the levels of beta-lactams by interfering with renal excretion? (but combination sometimes used intentionally in severe infections to increase antibiotic levels)

Answer 29

Probenecid