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Foundations 3 > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Beta-Lactam Mechanism of activity

A

kills bacteria by interfering with the synthesis of the bacterial cell wall

Binds to penicillin binding proteins (PBPs)

activity is limited to cells that are actively producing cell walls

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2
Q

Beta-Lactam mechanism of resistance

A

1) enzymatic destruction through beta lactamases (penicillinases in S. areus penicillin resistance)
2) alteration of penicillin-binding proteins (low-affinity PBP in MRSA called PBP2a)

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3
Q

Name the two major categories under Beta-Lactams.

A

Penicillins and Cephalosporins

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4
Q

Name the penicillin subclasses. What is the cellular target for all of these subclasses? What are the toxicities? Any exceptions?

A
  • Natural penicillins
  • Anti-staphylococccal penicillins
  • Aminopenicillins
  • Anti-speudomonal penicillins
  • Beta-lactam/Beta-lactam inhibitor combinations

Cellular target - Cell wall, inhibits cross-linking

Toxicities - rash, hypersensitivity, drug fever, antibiotic-associated diarrhea, C. difficile colitis, bone marrow suppression, seizures with high CNS levels, Coombs test, intersitital nephritis, anaphylaxis, allergic reactions

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5
Q

Natural penicillins

A
  • primarily for gram-positive bacteria
  • streptococcal infections (S. pyogenes, S. pneumoniae, enterococci)
  • will also cover N. meningitidis, Syphilis, and Listeria
  • will not cover most S. aureus because of penicillinase

ex. penicillin G (iv) and penicillin V (po)

Beta-Lactam, Penicillin

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6
Q

Anti-staphylococcal penicillins

A
  • not hydrolyzed by penicillinases or other beta-lactamases produced by S. aureus
  • used to treat MSSA
  • do not cover enterococci
  • note: workhorse for serious staphylococcal infections - endocarditis, osteomyelitis

ex. axacillin (iv), nofacillin (iv), dicloxacillin (po)

Beta-Lactam, Penicillin

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7
Q

Aminopenicillins

A
  • inactivated by many beta-lactamases
  • Gram-positive coverage similar to natural penicillins
  • covers some gram-negative infections
  • covers enterococci, L. monocytogenes, E. coli, Salmonella spp, and H. influenzae
  • increased activity due to ability to penetrate gram-negative outer membranes

ex.amoxicillin (po), ampicillin (iv and po)

Beta-Lactam, Penicillin

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8
Q

Anti-pseudomonal penicillins

A
  • Gram-positive coverage similar to natural penicillins, stronger gram-negative coverage
  • nosocomial gram-negative infections, including Pseudomonas
  • also covers many enterobacteriaceae

ex. piperacillin (iv), ticarcillin (iv)

Beta-Lactam, Penicillin

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9
Q

Beta-lactam/Beta-lactamase inhibitor combinations

A
  • gram-positive coverage
  • improved gram negative coverage and anaerobic activity due to the beta-lactamase inhibitor
  • covers S. aureus (MSSA)
  • covers gram-negatives including E. coli, K. pneumoniae, and Proteus mirabilis

ex. amoxicillin/clavulanate (po), ampicillin/sulbactam (iv), piperacillin/tazobactam (iv)

Beta-Lactam, Penicillin

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10
Q

Name the cephalosporin subclasses. What is the cellular target for all of these subclasses? What are the toxicities? Any exceptions?

A
  • 1st generation
  • 2nd generation
  • 3rd generation
  • 4th generation

Cellular target - cell wall, inhibits cell-wall cross-linking

Toxicities - rash, hypersensitivity (5-10% cross-reactivity with penicillins), antibiotic associated diarrhea, C. difficile colitis, neurotoxicity/seizures

  • cefepime notorious for neurotoxicity
  • ceftriazone assocciated with gallbladder sludge (caldium-ceftriazone salt percipitate)
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11
Q

1st generation

A
  • good activity against gram-positive organisms, including methicillin-susceptible S. aureus
  • most active cephalosporins against GPC, including MSSA (not enterococci)
  • covers gram-negatives such as E. coli, K. pneumoniae, and Proteus mirabilis

ex. cefazolin (iv), cephalexin (po)

note: cefazolin is common agent for surgical prophylaxis given skin coverage and some gram-negative

Beta-lactams, Cephalosporin

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12
Q

2nd generation

A
  • More gram-negative and less gram-positive activity
  • some in this group are active against anaerobes (cephamycins)

ex. cefuroxime (iv and po)

Beta-lactams, Cephalosporin

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13
Q

3rd generation

A
  • very active against most streptococci (except enterococci) and MSSA
  • good gram-negative coverage vs. Enterobacteriaceae but not Pseudomonas (except for ceftazidime)

ex. ceftriaxone (iv), cefixime (po), ceftazidime (iv)

note: ceftazidime is active against Pseudomonas and many nosocomial gram-negatives, but has no action against gram-positive or anaerobic activity

Beta-lactams, Cephalosporin

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14
Q

4th generation

A
  • maintains gram-positive coverage of all earlier generations
  • enhanced gram-negative and anti-pseudomonal coverage
  • remains active against many beta-lactamases produced by gram-negative organisms because of the zwitter-ion structure
  • very active against most streptococci (except enterococci) and MSSA

ex. cefepime (iv) and ceftaroline (iv)

note: ceftaroline is the only beta-lactam with activity against MRSA and some activity against Enterobacteriaceae

Beta-lactams, Cephalosporin

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15
Q

Monobactams

A
  • no gram-positive or anaerobic activity
  • active against Pseudomonas

ex. aztreonam

note: can be used in patients with allergy to penicillins/carbapenems

Toxicity: rash, hypersensitivity, antibiotic-associated diarrhea, C. difficile colitis, seizures with high CNS levels

Beta-lactam

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16
Q

Carbapenems

A
  • very broad gram-positive activity (including MSSA and enterococci)
  • anaerobic and gram-negative activity for Enterobacteriaceae, Pseudomonas, Acinetobacter

ex. imipenem (iv), meropenem (iv), doripenem (iv), ertapenem (iv)

note 1: ertapenem is not active against Pseudomonas

note 2: most reliable agents for Enterobacteriaceae with extended spectrum beta-lactamases

Toxicity: rash, hypersensitivity, antibiotic-associated diarrhea, C. difficile colitis, seizures with high CNS levels

Beta-lactams

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17
Q

Glycopeptides - Vancomycin mechanism of activity

A

inhibits bacterial cell wall synthesis, but at a different point than the beta-lactams

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18
Q

Glycopeptides - Vancomycin mechanisms of resistance

A

change in peptidoglycan with reduced binding to vancomycin - terminus altered to D-ala-D-lactate or D-ala-D-serine

production of thick cell wall with increased or false targets for vancomycin

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19
Q

Glycopeptides - Vancomycin spectrum of activity and toxicity

A
  • Gram-positive coverage only - aerobic and anaerobic
  • includes methicillin-resistant S. epidermidis, MRSA, and enterococci (not VRE)
  • intravenous vancomycin commonly used for serious infections of gram-positive organisms
  • oral vancomycin is not absorbed systmically, only used for infections within the intestinal lumen, primarily C. difficile
  • almost all gram-negatives are resistant

Toxicity: Red Man’s Syndrome/infusion reaction - not an allergy, nephrotoxicity, ototoxicity, bone marrow suppression

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20
Q

Lincosamides - Clindamycin mechanism of activity

A

inhibits proteins ynthesis by binding to the 50S subunit of the ribosome

blocks peptide bond formation, binding site is close to the site for erythromycin, shared resistance

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21
Q

Lincosamides - Clindamycin mechanism of resistance

A

methylation of the 50S subunit prevents clindamycin attachment

cross resistance with macrolides

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22
Q

Lincosamides - Clindamycin spectrum of activity and toxicity

A
  • good gram-positive and anaerobic activity
  • no gram-negative activity
  • active against most, but not all, MSSA and MRSA
  • good choice for empiric treatment of skin and soft tissue infections because of coverage for both streptocci and staphylococci
  • good oral bioavailability so may be used for outpatient therapy

toxicity: rash, antibiotic-associated diarrhea, C. difficile colits, esophagitis, hepatitis

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23
Q

Folate Antagonists - Trimethoprim-Sulfamethoxazole mechanism of action

A

blocks sequential steps in folate metabolism, synergistic combination

sulfonamides - compete with PABA for dihydropteroate synthas

trimethoprim - inhibits dihydrofolate reductase

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24
Q

Folate Antagonists - Trimethoprim-Sulfamethoxazole mechanisms of resistance

A

increased PABA concentration

enzymes with reduced affinity

loss of permeability

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25
Q

Folate Antagonists - Trimethoprim-Sulfamethoxazole spectrum of activity and toxicity

A
  • Gram-positive activity
  • S.aureus, including MRSA
  • some streptococci, but not reliable for causes of cellulitis
  • Listeria monocytogenes
  • Some Gram-negative activity
  • enterobacteriaceae - acquired resistance in E. coli and others now limits use as first line for urinary tract infection

Toxicity: rash, hypersensitivity, Stevens-Johnson Syndrome, and toxic epidermal necrolysis, aseptic meningitis, hepatitis, bone marrow suppression, hyperkalemia, elevated creatinine

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26
Q

Oxazolidinones - Linezolid mechanism of activity

A

inhibits protein synthesis by binding to 23S portion of 50S subunit

prevents formation of ribosomal complex that initiates protein synthesis

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27
Q

Oxazolidinones - Linezolid mechanism of resistance

A

enterococci and staphylococci resistance due to point mutations in 23S rRNA

requires mutations in two or more copies

28
Q

Oxazolidinones - Linezolid spectrum of coverage and toxicity

A
  • good gram-positive activity
  • active against streptocci and staphylococci
  • MRSA and VRE are susceptible
  • no gram-negative activity
  • no anaerobic activity
  • covers Mycobacterium tuberculosis and others

Toxicity: bone marrow suppression, peripheral neuropathy, serotonin syndrome (do not take with SSRIs), thrombocytopenia

29
Q

Lipopetide - Daptomycin mechanism of activity

A

binds to cell membrane

causes depolarization due to K+ efflux

depolarization disrupts cellular processes and leads to cell death

no resistance mentioned

30
Q

Lipopetide - Daptomycin spectrum of activity and toxicity

A
  • only gram-positive activity
  • active against streptococci and staphylococci
  • active against MRSA and VRE
  • cannot use in pulmonary infections due to being inactivated by pulmonary surfactant

Toxicity: muscle toxicity (myopathy, rhabdomyolysis), eosinophilic pneumonia

31
Q

Streptogrammins - quinupristin-dalfopristin

A

mechanism

  • binds to 50S ribosomal subunit and blocks peptide chain elongation

spectrum

  • bacteriostatic against E. faecium
  • bactericidal against S. aureus (including MRSA)
  • not active against E. faecalis

toxicity

  • phlebitis, arthralgias, myalgias, GI upset, elevated bilirubin

note: may have a role in treatment failure of first line agents vs. MRSA or VRE, not commonly used

32
Q

Rifamycin - Rifampin

A

mechanism

  • inhibits DNA-dependent RNA-polymerase, preventing chain initiation

spectrum

  • S. aureus, including MRSA
  • used in combination for Mycobacterium tuberculosis

toxicity

  • hepatitis, reddish discoloration of body fluids, rash, numerous drug-drug interactions

note: penetration into biofilms makes this useful for prosthetic material infections due to S. aureus

33
Q

Tetracyclines

A

mechanism

  • binds to 30S ribosomal subunit and blocks binding of aminoacyl RNA

spectrum

  • S. aureus, including MRSA
  • Chlamydia, Mycoplasma, Lyme disease, Tularemia, Brucella, Rickettsiae

toxicity

  • GI upset, diarrhea, photosensitivity, vestibular symptoms, increased skin pigmentation, tooth discoloration in children
  • ex. doxycycline (iv and po) and minocycline (po)*
34
Q

factors that influence whether the antibiotic is right

A

speed

IV vs. oral

breadth of empiric therapy

antibiotic resistance of pathogen

MIC of the effective antibiotic for the pathogen(s)

35
Q

steps take for patients in septic shock or severe sepsis

A

1) aggressive fluid resuscitation wtihin the first six hours
2) cultures and imaging studies, at least 2 sets of blood cultures
3) within the first hour after sepsis is identified, adminsiter broad, effective antimicrobials that has Gram positive and Gram negative coverage

36
Q

SIRS criteria

A

Systemic Inflammatory Response Sydrome

2 or more of the following:

  • Temp >38 or < 36
  • heart rate > 90
  • respiratory rate > 20 or PaCO2 < 32mmHg
  • WBC > 12,000/mm3 or <4000/mm3
37
Q

sepsis

A

SIRS + source of infection present or suspected

38
Q

severe sepsis

A

sepsis with organ dysfunction, hypoperfusion, hypotension, and/or lactic acidosis

39
Q

septic shock

A

severe sepsis with hypotension despite adequate fluid resuscitation

40
Q

sequestered vs. non-sequestered site of infection

A

non-sequestered - site that has no anatomic or physiologic barriers to the antibiotic such as well perfused skin, kineys, lungs

sequestered - prostate, brain, bone, large abscess, poorly perfused site (severe trauma)

41
Q

broad spectrum antibiotic combination for penicillin-allergic patients

A

vancomycin + aztreonam + metronidazole

42
Q

Fluoroquinolones mechanism of action

A

inhibits DNA gyrase in Gram-negative organisms

inhibits Topoisomerase IV in Gram-positive organisms

43
Q

Fluoroquinolones mechanism of resistance

A

1) a single point mutation in the bacterial chromosome can result in resistance by altering affinity of the antibiotic to bind to the target enzyme, most common mechanism of resistance
2) plasmids can code for efflux pumps

44
Q

Fluoroquinolones spectrum of activity and toxicity

A
  • all have Gram-negative activity
  • activity against intracellular organisms such as Chlamydophila pneumoniae, Legionella spp., and Mycoplasma pneumoniae
  • S. pneumoniae activity
  • MSSA, though resistance may develop on therapy
  • good activity against Enterobacteriaceae and Pseudomonas

Toxicity

  • tendonitis/tendon rupture, antibiotic-associated diarrhea, C. difficile colitis, CNS toxicity, QTc prolongation

note 1: ciprofloxacin is very useful against genitourinary infections, bu tresistance is common due to overuse

note 2: respiratory fluoroquinolones can be used as a single agent for community acquired pneumonia (active against typical and atypical organisms)

ex. ciprofloxacin (iv and po), levofloxacin (iv and po), and moxifloxacin (iv and po)

45
Q

Aminoglycosides mechanism of action

A

binds irreversibly to the 30S ribosome within the cytoplasm and inhibit protein synthesis by preventing the translocation of peptidyl-t-RNA

bacterial cell death depends on high concentrations of the drug reaching the site of infection, and oxygen is necessary

postantibiotic effect - after the serum concentration ahs fallen, residual intracellular drug remains bacteriocidal

46
Q

Aminoglycosides mechanism of resistance

A

1) drug inactivation, plasmid that encodes for an enzyme that alters the drug
2) rare mutations that alter the structure of the ribosomes so that binding is impaired

natureal resistance:

1) bacteria is an anaerobe and growing in an anaerobic enviroment, drug can’t cross the cytoplasmic membrane
2) ribosome has low affinity for the drug

47
Q

Aminoglycosides spectrum of activity and toxicity

A
  • targets aerobic Gram-negatives
  • active against Pseudomonas
  • used as a second agent for serious staphylococcal or enterococcal infections
  • works against S. aureus

Toxicity: nephrotoxicity, ototoxicity, neuromuscular blockade

ex. gentamicin (iv), tobramycin (iv), amikacin (iv) - know these!

48
Q

Nitroimidazoles - Metronidazole mechanism of action and toxicity

A

intracellularly generates short-live reactive intermediates that damage DNA by electron transfer system

49
Q

Nitroimidazoles - Metronidazole spectrum of activity

A
  • active against anaerobic bacteria
  • Bacterioides, C. difficile, Trichomonas, Giardia, E. histolytica

Toxicity: headaches, nausea, metallic taste, disulfuram-like reaction, neuropathy with prolonged use

50
Q

Macrolides mechanism of action

A

binds to the 50S ribosomal subunit and blocks peptide bond formation

51
Q

Macrolides spectrum of coverage and toxicity

A
  • Gram positive - S. pneumoniae
  • Gram-negative - H. influenzae, Neisseria spp., B. pertussis, Campylobacter
  • Atypical - Mycoplasma, Legionella, Chlamydia

Toxicity: GI upset, diarrhea, QTc prolongation leading to rosades des pointes, ventricular tachycardia and sudden death

ex. erythromycin (po), azithromycin (iv and po), clarithromycin (po)

52
Q

Type I Antibiotic Allergy

A

Immediate

Mechanism

  • IgE mediated
  • binds to mast cells and basophils
  • histamine, leukotrienes, and prostaglandins released

Symptoms

  • urticaria, angioedema, anaphylaxis
  • onset is rapid

Management

  • epinephrine, antihistamines, H2-blocekrs, glucocorticoids
53
Q

Type II Antibiotic Allergy

A

Cytotoxic

Mechanism

  • Antibody mediated (usually IgG)
  • leads to tissue destruction

Symptoms

  • immune hemolytic anemia
  • thrombocytopenia
54
Q

Type III Antibiotic Allergy

A

Immune complex

Mechanism

  • Immune complex disease
  • soluble immune complex (IgG boudn to drug)
  • deposition and complement activation

Symptoms

  • serum sickness
  • drug fever
  • vasculitis
55
Q

Type IV Antibiotic Allergy

A

Delayed

Mechanism

  • T cell mediated
  • sensitized lymphocytes

Symptoms

  • Maculopaopular exanthem (outward from central location)
  • contact dermatitis
  • fixed drug eruption
  • Stevens-Johnson Syndrome
  • Toxic Epidermal Necrolysis
56
Q

SJS and TEN

A

Stevens Johnson Syndrome and Toxic Epidermal Necrolysis

severe idiosyncratic reactions characterized by fever, mucocutaneous lesions, and sloughing of the epidermis

both are generally triggered by medications, antibiotics being the most likely

57
Q

Streptogrammins - quinupristin-dalfopristin (iv) mechanism of action

A

binds to 50S ribosomal subunit, blocks peptide chain elongation

58
Q

Streptogrammins - quinupristin-dalfopristin (iv) spectrum of activity and toxicity

A
  • bacteriostatic against E. faecium (including VRE)
  • bactericidal vs. S. aureus (including MRSA)
  • not active against E. faecalis

Toxicity: phlebitis, arthralgias, myalgias, GI upset, elevated bilirubin

note: may have role in treatment failure of first line agents vs. MRSA or VRE, not commonly used

59
Q

Chloramphenicol - chloramphenicol (iv and po) mechanism of action

A

binds to 50S ribosomal subunit and blocks aminoacyl tRNA attachment

60
Q

Chloramphenicol - chloramphenicol (iv and po) spectrum of activity and toxcitiy

A
  • Streptococci
  • H. influenzae, Neisseria spp.
  • Salmonella typi, Brucella spp., Bordetella pertusis
  • most anaerobes
  • Rickettsiae

Toxicity:

  • reversible bone marrow toxicity, aplastic anemia, Gray baby syndrome

note: very infrequently used int he US

61
Q

Glycyclcyline - tigecycline (iv) mechanism, spectrum of action, and toxicity

A

Tetracycline subclass

mechanism

  • binds to 30S ribosomal subunit, blocks binding of aminoacyl tRNA

Spectrum

  • MSSA, MRSA, VRE
  • active against many gram-negatives, including some MDR Acinebacter and carbapenem-resistant Enterobacteriaceae (CRE)

not active against Pseudomonas

Toxicity: nausea and vomiting, photosensitivity, pancreatitis

note: bacteriostatic and does not achieve high serum levels, so despite its very broad activity, it is less useful for serious infections

62
Q

Urinary antiseptics - nitrofurantoin (po) mechanism of action

A

inhibits bacterial acetyl-coenzyme A, interfering with the organism’s carbohydrate metabolism

63
Q

Urinary antiseptics - nitrofurantoin (po) spectrum of activity and toxicity

A
  • Enterococci, including VRE
  • S. sapprophyticus
  • gram negatives, including E. coli

Toxicity: interstitial pneumonia wiht fibrosis, hepatitis, rash, polyneuropathy

note: useful first line agent for UTI, except in elderly or others with reduced CrCl

64
Q

Polymixins mechanism of action

A

disrupts the cell membrane permeability by charge alteration

65
Q

Polymixins spectrum of activity and toxicity

A
  • Gram-negative activity, including Enterobacteriaceae and Pseudomonas

Toxicity: nephrotoxicity, neuromuscular blockade

note: used in combination against very resistant organisms - MDR Pseudomonas, MDR Acinetobacter, carbapenem-resistant Enterobacteriaceae (CRE)

ex. colistin (iv) and polymixin B (iv)

66
Q

antibiotics with time-dependent activity

A

Beta-lactams

Carbapenems

Vancomycin

Clindamycin

Linezolid

67
Q

antibiotics with concentration-dependent activity

A

aminoglycosides

fluoroquinolones

metronidazole

Foundations 3 (20 decks)

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