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Micro Exam 1 > Pogue: Antimicrobials IIb > Flashcards

Pogue: Antimicrobials IIb Flashcards

1
Q

Macrolides

MOA:

Bacteriostatic or Bactericidal?

A

Bind to the 50S subunit of the ribosome

Bacteriostatic

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2
Q

Macrolides

Agents (of clinical relevance)

A

Erythromycin (IV/PO)
Clarithromycin (PO)
Azithromycin (IV/PO)

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3
Q

Macrolides

Spectrum of activity

A

The respiratory pathogens

C.trachomatis: causes Chlamydia

Mycobacterium avium complex (MAC)

H.pylori: clarithromycin

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4
Q

The respiratory pathogens:

A 
Streptococcus
H.influenzae
M.catarrhalis
Mycoplasma pneumonia
Chlamydia pneumonia
Legionella pneumophilia
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5
Q

What treats against MAC?

A

Mycobacterium avium complex (MAC): clarithromycin and azithromycin

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6
Q

What treats H.pylori?

A

Clarithromycin

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7
Q

Macrolides

Side effects
Biggest class concern:
Worst with what? Why?
Much less with what?

A

Biggest class concern: nausea/vomiting/diarrhea

–Worst with erythromycin as it binds to the motolin receptor in the GI tract
•Pearl: erythromycin actually used as promotility agent in hospital for severe constipation

–Much less with azithromycin

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8
Q

Macrolides

Other side effects:

A 
QT prolongation (pro-arrhythmia)
Rare hepatotoxicity
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9
Q

Macrolides

Clinical Uses:

A

Respiratory Tract Infections: azithromycin first line for CAP (also used in traceobronchitis, COPD exacerbations)

H.pylori: clarithomycin part of standard therapy

Mycobacterial regimens: clarithromycin and azithromycin

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10
Q

Macrolide Resistance:

A

Target-Site Modification: change in the 50S subunit binding site

Decreased Concentration in the Cell: efflux pumps

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11
Q

Macrolide

IV dose =
Azithromycin half life:
Metabolism
DDIs
Renal dosing
A

IV dose = PO dose
Azithromycin long half-life
–~ 72 hours; allows shorter course of the drug

Metabolism
–Inhibitors and substrates of CYP3A4

Many drug interactions

No renal dose adjustment needed

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12
Q

Macrolide

DDIs:

A

Erythromycin and clarithromycin are the big players here

Azithromycin much less

Why azithromycin is the workhorse for this class

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13
Q

What is first line medication for CAP?

A

Azithromycin

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14
Q

What are ketolides?

What is Telithromycin?

A

Ketolides are antibiotics belonging to the macrolide group

Telithromycin is the first ketolide antibiotic to enter clinical use and is sold under the brand name of Ketek.

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15
Q

Ketolides: Telithromycin

General:

Spectrum of Activity:

Clinical Use:

A

Derivative of macrolides

Spectrum of Activity:
- Similar to azithromycin, with enhanced activity against S.pneumo

Clinical Use:

  • Originally thought to be a niche drug for CAP
  • High rates of hepatotoxicity has limited use clinically
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16
Q

TETRACYCLINES:

MOA:

Bacteriostatic or Bactericidal?

A

MOA: ribosomal antibiotic that works on the 30S subunit of the ribosome

Bacteriostatic

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17
Q

TETRACYCLINES:

Pharmacokinetics:

A

Highly lipophilic: penetrates tissues well

Not highly renally eliminated: but still sufficient for UTI

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18
Q

Tetracycline Agents (3):

What is used for SIADH?

A

Tetracycline (PO)

Doxycycline and Minocycline (IV/PO): most often used

Demeclocycline (PO): used for SIADH

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19
Q

Doxycylin and Minocycline

Spectrum of activity:
G+
G-
Anaerobic activity
Miscellaneous: has activity against (2)
A

Gram (+) Activity:
S.pneumo
S.aureus (including MRSA)
enterococcus

Gram (-) Activity:
H.influenzae
M.catarrhalis
may also have activity against enterobacteraciae (including MDRO)

Anaerobe Activity: variable

Miscellaneous: has activity against
o Atypical pneumonia pathogens
o Organisms associated with animal bites (Lyme disease)

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20
Q

Clinical Use (Doxycyclin and Minocyclin) (3):

A

Respiratory tract infections (including CAP)

UTIs

Skin and soft tissue infections (particularly when community acquired-MRSA is a concern)

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21
Q 
Tetracycline 
Adverse Effects (3):
A

N/V/D: lessened with food

Binding to growing teeth and bones: avoid if less than 8 years old

Photosensitization

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22
Q

Tetracycline

Drug Interactions:

A

Chelate with divalent and trivalent cations

Do not take with multivitamins!

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23
Q

What are Glycylcyclines?

What is Tigecycline?

A

Glycylcyclines are a new class of antibiotics derived from tetracycline.

Tigecycline is a glycylcycline antibiotic

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24
Q

Tigecycline:

MOA:

Pharmacokinetics:

A

First in this new class that is a derivative of the tetracyclines

MOA: same as tetracycline (bind 30S subunit of ribosome); also bacteriostatic (?)
o However, has a different structure and has the ability to overcome some of the tetracycline-resistance mechanisms (efflux pumps, target-site alterations)

Pharmacokinetics:
- Same as tetracycline

25
Q

Tigecycline

Spectrum of Activity:
G+
G-
Anaerobic
Notable holes
A

Gram (+) Activity: broad (includes MRSA and VRE)

Gram (-) Activity: similar to tetracyclines, but also includes resistant organisms (ESBL, Acinetobacter)

Anaerobic Activity: some coverage

Notable Holes: pseudomonas and proteus (and providencia)

26
Q

Tigecycline

Clinical use (3):

Adverse reactions:

A

Clinical Use:

Last line option for many nasty Gram (-) bugs:
o Carbapenem-resistant acinetobacter
o Klebsiella

Polymicrobial wounds: including MRSA or VRE

2nd line therapy for pts with penicillin allergies for multiple disease states

Adverse Reactions:

  • Nausea and vomiting: 20% of patients
  • Pancreatitis: few cases noted in post marketing analysis
27
Q

LINCOSAMIDES

MOA:

Bacteriostatic or Bactericidal?

Agents (2):

A

Acts on 50S subunit of the ribosome to prevent protein synthesis

Bacteriostatic

Lincosamide Agents:

  1. Lincomycin: been completely replaced by clindamycin (increased activity)
  2. Clindamycin
28
Q

Spectrum of Activity (Clindamycin):

G+
G-
Anaerobes

A

Gram (+) Activity: S.aureus (including MRSA), Streptococcus (usually)
o Note: has toxin suppression activity and necrotizing Gram (+) infections

Gram (-) Activity: NONE

Anaerobes: good (better for oral anaerobes than lower GI anaerobes)

29
Q

Clinical Uses (Clindamycin) (3):

A

Skin infections: because of staphylococcus (including MRSA) and streptococcus coverage

Aspiration pneumonia: since anaerobes are thought to play a role (but NO Gram (-) coverage)

Alternative for anaerobic coverage

30
Q

Side Effects (Clindamycin):

A

Diarrhea: in both PO and IV formulations

Nausea

C.difficile Diarrhea: used to be the number one antibiotic associated with C.diff (now FQ and other broad spectrum agents)

31
Q

Macrolide-Lincosamide-Streptogramin (MLS) resistance seen in what?

S.aureus can posses:

Can lead to:

How do you detect presence of erm gene?

A

Macrolide-Lincosamide-Streptogramin (MLS) Resistance in S.aureus:

S.aureus can posses an erm gene that can encode resistance to all 3 classes (all bind 50S subunit)

Can lead to inducible clindamycin resistance when isolate says “erythromycin resistant and clindamycin susceptible”

Can use a special D test to detect presence of the erm gene

32
Q

Sulfonamides:

MOA
What does PABA do?
Bacteriostatic or Bactericidal?
Most commonly used agent:

A

MOA: structural analog of PABA, which blocks the production of dihydrofolic acid

Folic acid –> DHF –> THF –> Thymidines, purines

Bacteriostatic

Most commonly used agent: sulfamethoxazole (combined with trimethoprin= BACTRIM)

Bactrim (TMP/SMX): together, the two become bactericidal (synergy)

33
Q

What is Trimethoprin?

A

Inhibitor of dihydrofolic acid reductase (next step in the production of purines and DNA); also bacteriostatic

34
Q

Spectrum of Activity (TMP/SMX):

G+
Anaerobic
Miscellaneous:

A

Gram (+): staphylococcus (including MRSA), some streptococcus (notably lacks group B strep), no enterococcus

Anaerobic: minimal

Miscellaneous:
o Listeria and Nocardia
o DOC for Stenotrophomonas maltophilia

35
Q

What is the DOC for Stenotrophomonas maltophilia?

A

TMP/SMX

36
Q

Spectrum of Activity (TMP/SMX):

G-
Pseudomonas

A

Gram (-):

Enteric Gram negatives (variable; Klebsiella, Proteus, E.coli)

SPICE organisms (limited clinical use for these)

No pseudomonas coverage

37
Q

Clinical Applications (TMP/SMX):

A

Outpatient UTIs: most commonly used agent for these

Skin infections when MRSA is a concern: but remember, no coverage of group B strep

DOC for many nasty infections:
o PCP (pneumocystis) pneumonia
o Stenotrophomonas maltophilia
o Nocardia

Treatment of multi-drug resistant Gram-negatives: role still debated

38
Q

What is the most commonly used agent for outpatient UTIs?

A

TMP/SMX

39
Q

What is the DOC of Nocardia and PCP Pneumonia?

A

TMP/SMX

40
Q

TMP/SMX

Side Effects:

A

Hypersensitivity Reactions: most common agents that cause these (~3% of patients)
- Simple rash –> Severe skin reactions (SJS/TEN)

High concentrations can crystallize in the urine (Rare)

TMP SEs:
o Bone marrow suppression: anemia, leucopenia, and granulocytopenia
o Hyperkalemia

41
Q

TMP/SMX

DDIs:

A

Increased INR (How thin blood is) when given with warfarin: INR is the measurement that indicates if warfarin is at therapeutic levels or not

42
Q

NITROIMIDAZOLES:

MOA

Pharmacokinetics:

Agents:

A

MOA: not clearly defined; interaction with DNA that causes a loss of the helical structure and strand breaking, leading to cell death

Pharmacokinetics:

  • ~100% bioavailability
  • Minimal renal elimination

Agents:

  • Metronidazole
  • Tinidazole
43
Q

Spectrum of Activity (Metronidazole):

A

ANAEROBES ONLY: better for lower GI anaerobes vs. mouth anaerobes (opposite of clindamycin)
o DOC for C.difficile**
- Some parasitic activity: T.vaginalis

44
Q

What is the DOC of C.difficile?

A

Metronidazole - Mild

Vanco - Severe

45
Q

Clinical Applications (Metronidazole):

Side Effects:

Drug Interactions:

A

Clinical Applications (Metronidazole):

  • Anaerobic coverage for nosocomial patients
  • DOC for C.diff
  • T.vaginalis

Side Effects:

  • N/V
  • Metallic taste
  • Disulfuram reaction with ethanol
  • Peripheral neuropathies (rare)

Drug Interactions:
- Increased INR when given with warfarin

46
Q

Drugs with anaerobic coverage (8)

A 
Metronidazole
Penicillin
B-lactam/B-lactamase inhibitors
–Piperacillin/tazobactam, ampicillin/sulbactam
Clindamycin
Cephamycins
Carbapenems
Moxifloxacin
Tetracyclines (some)
47
Q

RIFAMPIN

MOA:

Pharmacokinetics:

Spectrum of Activity:
G+:
G-:
Miscellaneous:

A

MOA: binds to b-subunit of DNA-dependent RNA polymerase, blocking RNA synthesis

Pharmacokinetics:

  • ~100% bioavailability (IV dose=PO dose, but food may delay absorption)
  • No renal dosing necessary

Spectrum of Activity:

Gram (+): S.aureus (including MRSA) and streptococcus; not used as monotherapy

Gram (-): used in combination with cell wall agent for synergy; minimal activity alone

Miscellaneous: standard therapy for mycobaterial infections

48
Q

RIFAMPIN

Clinical Application:

Side Effects:

A 
Clinical Application:
-	Synergy: 
o	Severe staph infections
o	Multi-drug resistant gram (-) bacilli
-	Mycobacterial infections: part of standard TB regimen

Side Effects:

  • Hepatotoxicty (HIGHLY)**
  • Discolored fluids
49
Q

RIFAMPIN

Drug Interactions:

A

STRONG inducer of multiple CYP450 isoenzymes**

Contraindicated with many HIV meds

Significant interactions with:
o Antifungals
o Anti-hypertensives
o Statins

50
Q

What is part of the standard therapy for mycobaterial infections?

A

Rifampin

51
Q

POLYMIXINS:

MOA:

Bacteriostatic or Bactericidal?

Why was use abandoned? What lead to re-emergence?

A

MOA: Cationic detergent that damages the cytoplasmic membrane, leading to leakage of intracellular substances and rapid cell death

Electrostatically interacts with the LPS outer membrane of G- organisms

Bactericidal

Originally utilized in the 1950s
Associated with high rates of nephrotoxicity and neurotoxicity, so use abandoned;
Multi-drug resistance Gram negatives in the 1990s lead to re-emergence

52
Q

POLYMIXINS

Agents:

Pharmacokinetics:

A

Agents:

  • Colistin (IV)
  • Polymixin B (IV,PO,topical)

Pharmacokinetics:
- Poorly understood

53
Q

POLYMIXINS

Spectrum of Activity:

G+
G-
Anaerobic

A

Gram (+): NONE

Gram (-):

Pseudomonas, A.baumannii, K.pneumoniae, E.coli;

No activity against serratia and proteus

Anaerobic: NONE

54
Q

Clinical use

Adverse events

DDIs

A

Clinical Use:
- Mulit-drug resistant gram (-) organisms in the hospital: when there are no other options!
o Usually pseudomonas, A.baumannii, and K.pneumoniae (KPC- carbapenamase producing organism)

Adverse Events:

  • Nephrotoxicity: up to 40% of patients; dose dependent and reversible
  • Neurotoxicity: parasthesias

Drug Interactions:
- Additive toxicities

55
Q

Antipseudomonal Agents (Full List)

A 
Piperacillin, Piperacillin/Tazobactam
Cefepime, Ceftazadime
Meropenem, Imipenem, Doripenem
Aztreonam
Gentamicin, Tobramycin, Amikacin
Ciprofloxacin, Levofloxacin
Polymixins
56
Q

CHLORAMPHENICOL:
MOA:

Clinical Use:

Side Effects:

A

MOA: ribosomal 50S inhibitor

Clinical Use: not clinically used any more due to toxicity

Side Effects:

  • Bone Marrow Suppression: dose-dependent
  • Aplastic Anemia: non-dose dependent
  • Gray-Baby Syndrome
57
Q

Gray-Baby Syndrome:

A

SE of Chloramphenicol

Lack of an enzyme in phase II metabolism of the drug; leads to accumulation of a toxic metabolite (causes graying of the skin and cyanosis, among other symptoms)

58
Q

NITROFURANTOIN:

MOA:
Spectrum of Activity:
Clinical Use:
Side Effects:
Contraindications:
A

MOA: inhibition of a variety of bacterial enzyme systems interfering with metabolism

Spectrum of Activity: organisms causing UTIs

Clinical Use: only to treat lower UTIs (First line)

Side Effects: rare inflammatory lung process

Contraindications: cannot use if GFR <60mL/min (completely filtered by the kidney)

59
Q

DAPSONE:

MOA:
Clinical Use:
Side Effects:

A

MOA: antagonist of PABA (similar to sulfa drugs)

Clinical Use: prevention/treatment of PCP pneumonia when TMP/SMX cannot be used (ie. allergy)

Side Effects: hemolysis; generally infrequent but more common in patients with G6P deficiency

Micro Exam 1 (18 decks)

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