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Infectious Disease and Medical Microbiology > Antibacterial Therapy I > Flashcards

Antibacterial Therapy I Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

ADME

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

Absorption

A

Drugs that have >80% bioavailability, basically the same as IV
eg. fluoroquinolones, clindamycin, fluconazole, metronidazole

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3
Q

Distribution

A

Volume of distribution:

  • ratio of amount of drug in body to serum concentration of drug
  • not an anatomical space in body
  • can be altered by clinical factors (eg. protein binding, organ failure)
  • half life of drug determined by volume of distribution and organ clearance of drug
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4
Q

Metabolism

A
  • many antimicrobials undergo hepatic metabolism

- many inhibit or induce cytochrome 450 enzymes

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5
Q

Excretion

A
  • may need to alter dosage in their is renal impairment (reduced excretion results in longer half life)
  • ceftriaxone, metronidazole, moxifloxacin not renal eliminated
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6
Q

Antibacterial susceptibility testing

A
  • eg. broth dilution tests, disk diffusion tests, E tests
  • in vitro testing not representative of in vivo activity (does not account for immune system, site of inoculation, artificial growth conditions)
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7
Q

Bactericidal vs. bacteriostatic

A
  • bactericidal usually DNA synthesis or cell wall inhibitors
  • bacteriostatic usually protein inhibitors, requires functioning immune system to clear ix
  • cidal better for deal seated ix’s, but induces immune response
  • static better for slow growing bacteria
  • organism dependent whether it’s cidal or static
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8
Q

Concentration dependent agents

A
  • higher concentration results in higher killing of bacteria
  • better to give fewer higher doses
  • eg. fluoroquinolones, aminoglycosides
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9
Q

Time dependent agents

A
  • higher concentrations do result in higher killing, but maxes out at 4-5x MIC
  • better to give more frequent smaller doses
    eg. beta lactams
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10
Q

Post antibiotic effect

A
  • antibiotic continues to inhibit bacterial growth even after antimicrobial discontinued
  • allows for less frequent dosing
  • most have 1-2 hr PAE vs G+
  • aminoglycosides and fluoroquinolones have extended PAE vs G-
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11
Q

Peak/MIC

A
  • important parameter for concentration dependent agents

- Peak/MIC > 8 associated with best cure rates

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12
Q

Time/MIC

A
  • important parameter for time dependent agents

- Time over MIC > 40% associated with best cure rates

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13
Q

AUC/MIC

A

-important parameter for vancomycin, fluoroquinolones, aminoglycosides

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14
Q

Factors involved in choosing an antimicrobial (5)

A
  • Efficacy
  • Toxicity
  • Patient specific factors
  • Ease of administration
  • Cost
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15
Q

Efficacy

A
  • spectrum of activity, pharmacodynamic properties of agent
  • site of ix (likely causative organism, whether agent will reach sites, other treatments required to aid ix clearance)
  • local susceptibility patterns (antibiograms, don’t use agent that has greater than 10% resistance in community)
  • published evidence
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16
Q

Toxicity

A
  • all have risk of adverse rx, vary in type and severity

eg. C diff risky abx (cephalosporins, fluoroquinolones, clindamycin)

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17
Q

Patient specific factors

A
  • Hepatic, renal functioning
  • Age, weight, social factors
  • allergies
  • pregnancy
  • history of abx use
  • immune status
18
Q

Ease of administration

A

-less frequent oral dosing is best

19
Q

Cost

A
  • all else equal, consider cost

- oral forms usually cheaper

20
Q

Beta lactam MOA

A

-inhibits cell wall synthesis by binding penicillin binding proteins, preventing cross linking

21
Q

Betalactamases

A
  • produced by various bacteria against various types of beta lactams
  • can be plasmid or chromosomal
  • some are inducible
22
Q

Betalactamase inhibitor

A
  • eg. clavulanate, tazobactam
  • no antibacterial activity on their own
  • bind betalactamases and inhibit them
23
Q

Penicillin

A

-penicillins
S: Streptococci
CI: Bacterial pharyngitis, endocarditis

24
Q

Amoxicillin

A

Penicillins
S: Streptococci and Enterococcus faecalis
CI: otitis media, CAP, enterococcal ix’s

25
Q

Cloxacillin

A

Penicillins
S: MSSA
CI: Bacteremia, endocarditis, bone joint ix’s, SSTI

26
Q

Amoxicillin/clavulanate

A

Penicillins
S: G+, G-, anaerobes
CI: polymicrobial ix’s (eg. diabetic foot ulcer)

27
Q

Piperacillin/tazobactam or ticarcillin/clavulanate

A

Penicillins
S: G+, G-, Pseudo, anaerobes
CI: polymicrobial ix’s, febrile neutropenia, sepsis unknown source

28
Q

Cephalexin

A

Cephalosporin
S: MSSA, beta hemolytic Strep.
CI: SSTI

29
Q

Cefazolin

A

Cephalosporin
S: MSSA, E coli, Klebsiella, Proteus, Streptococci
CI: SSTI, Bone and joint ix’s, surgical prophylaxis

30
Q

Cefuroxime

A

Cephalosporin
S: Penicillin S S. pneumo, H. influenzae, M. catarrhalis
CI: respiratory ix’s, not first line

31
Q

Cefotaxime/Ceftriaxone

A

Cephalosporin
S: Penicillin I/R S. pneumo, G-, Streptococci
CI: SSTI, endocarditis, urosepsis

32
Q

Cefixime

A

Cephalosporin
S: Penicillin S Streptococci, G-
CI: UTI, gonorrhea

33
Q

Ceftazidime

A

Cephalosporin
S: Pseudo
CI: combo w/ aminoglycosides for severe Pseudo ix’s

34
Q

Cefepime

A

Cephalosporin
S: MSSA, Penicillin I/R S. pneumo, G+, G-. Pseudo
CI: combo w/ aminoglycosides for Pseudo, febrile neutropenia, polymicrobial ix’s

35
Q

Cephalosporins - No Activity vs. (2)

A
  • Enterococci

- MSSA

36
Q

Ertapenem

A

Carbapenem
S: G+, G-, anaerobes, ampC/ESBL producers
CI: polymicrobial ix’s w/ MDR

37
Q

Meropenem

A

Carbapenem
S: G+, G-, anaerobes, ampC/ESBL producers, Pseudo
CI: post-trauma or neurosurgical meningitis, polymicrobial ix’s w/ MDR

38
Q

Imipenem

A

Carbapenem
S: G+, G-, anaerobes, ampC/ESBL producers, Pseudo, E. faecalis
CI: intraabdominal, polymicrobial ix’s w/ MDR

39
Q

Carbapenem Spectrum and Usage

A
  • reserved for MDR ix’s
  • not first line
  • no activity vs. MRSA
40
Q

Penicillin allergy

A
  • less than 10% who report allergy have true anaphylactic reaction
  • not genetic
  • 50% will lose sensitivity in 5 years, 80% in 10 years
  • need to clarify allergy history
41
Q

Penicillin allergy cross-reactivity

A
  • related to R side chains of beta lactam
  • low cross reactivity between groups (eg. penicillins and cephalosporins)
  • if life-threatening non-IgE mediated allergy, do not use any beta lactams

Infectious Disease and Medical Microbiology (11 decks)

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