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Antimicrobials Flashcards

1
Q

Antibiotic MOAs and classes

A

Cell wall synthesis inhibitors:
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams

Peptidoglycan formation inhibitor (D-ala-D-ala binding):
- Glycopeptides/Vancomycin

Inhibit topoisomerase II and IV:
- Fluoroquinolones

30S ribosomal subunit:
- Aminoglycosides
- Tetracyclines

50S ribosomal subunit:
- Clindamycin
- Chloramphenicol
- Macrolides (Erythromycin)
- Linezolid

Folic acid synthesis inhibitors:
- Trimethoprim-sulfamethoxazole

Other:
- Metronidazole
- Lincosamides
- Anti-TB agents

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2
Q

Beta-lactam MOA

A

Beta-lactams bind to penicillin-binding-proteins (PBPs, aka transpeptidases) and block transpeptidase cross-linking of peptidoglycan in cell wall

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3
Q

Beta-lactam: bacterial mechanisms of resistance

A
  • cleavage of beta-lactam ring via beta-lactamases
  • alteration of binding site (PBP), seen in Staph aureus and Strep pneumoniae
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4
Q

General beta-lactam side effects

A
  • rash
  • GI upset
  • hypersensitivity reactions (types I-IV)
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5
Q

Beta-lactam drugs

A
  • Penicillins (penicillin G, ampicillin, amoxicillin, methicillin)
  • Cephalosporins (cephalexin, cefuroxime, ceftriaxone, cefepime)
  • Carbapenems (imipenem-cilastatin*, meropenem, doripenem)
  • Monobactams (atreonam)

*imipenem is combined with cilastatin, a dehydropeptidase inhibitor, which prevents breakdown of imipenem in kidneys

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6
Q

Carbapenem

A
  • resistant to β-lactamase
  • used to treat extended-spectrum beta-lactamase-producing bacteria (ESBL)
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7
Q

beta-lactam + beta-lactamase inhibitor combinations

A
  • Amoxicillin-Clavulanic acid
  • Ampicillin-Sulbactam
  • Piperacillin-Tazobactam

“-bactam”

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8
Q

Glycopeptides (Vancomycin) MOA

A

Inhibits peptidoglycan formation by binding to the D-ala-D-ala of the peptide terminus, inhibiting transglycosylation

Gold standard for treating MRSA and coagulase-negative Staph

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9
Q

Vancomycin: bacterial mechanisms of resistance

A

the last D-ala residue is replaced by D-lactate, so vancomycin cannot bind

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10
Q

Vancomycin side effects

A
  • nephrotoxicity
  • ototoxicity
  • Vancomycin flushing reaction / infusion reaction (mast cell degranulation with release of histamine, not a true allergy)
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11
Q

Ribosomal protein synthesis inhibitors

Buy “AT” 30, “CCEL” at 50

A

30S ribosomal subunit inhibitors:
A - Aminoglycosides (amikacin, gentamicin, streptomycin)
T - Tetracyclines (doxycycline, tetracycline)

50S ribosomal subunit inhibitors:
C - Clindamycin
C - Chloramphenicol
E - Erythromycin (Macrolide class)
L - Linezolid

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12
Q

Aminoglycoside MOA

A

binds to 30S ribosomal subunit, inhibiting initiation complex and leading to misreading of mRNA ==> mistranslation

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13
Q

Aminoglycoside bacterial method of resistance

A

bacterial transferases inactivate drug by acetylation, phosphorylation, adenylation

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14
Q

Aminoglycoside side effects

A
  • nephrotoxicity
  • ototoxicity
  • teratogenicity
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15
Q

Tetracycline MOA

A

binds to 30S ribosomal subunit and prevents attachment of aminoacyl-tRNA

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16
Q

Tetracycline side effects

(Doxycycline)

A
  • photosensitivity
  • drug deposits in bones/teeth ==> inhibition of bone growth and teeth discoloration in children
  • drug-drug interaction: divalent cations can bind to tetracycline and inhibit drug absorption

great for treating organisms that don’t gram-stain well
- gram-negative bacteria
- spirochetes & zoonotics

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17
Q

Tigecycline

A

tetracycline-derivative, binds to 30S ribosomal subunit

used for MRSA and VRE

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18
Q

Clindamycin MOA

A

blocks translocation at 50S subunit, preventing peptide chain elongation

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19
Q

Clindamycin side effects

A
  • C. diff overgrowth, causing Pseudomembranous Colitis
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20
Q

Chloramphenicol MOA

A

blocks peptidyltransferase at 50S subunit

not really used clinically anymore

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21
Q

Chloramphenicol side effects

A
  • anemia
  • gray baby syndrome: permature infants lack liver UDP-glucuronyltransferase
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22
Q

Macrolide (Erythromycin) MOA

A

blocks translocation by binding to 23s rRNA component of 50S subunit, preventing peptide chain elongation

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23
Q

Macrolide side effects

A
  • GI motility ==> vomiting
  • prolongation of QT interval ==> cardiac arrythmias
  • drug-drug interactions with erythromycin
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24
Q

Linezolid MOA

A

prevents formation of the initiation complex by binding to 23S rRNA of the 50S subunit

used to treat MRSA and vancomycin-resistant Enterococcus (VRE)

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25
Linezolid side effects
- bone marrow suppression ==> pancytopenia (decrease in RBCs, WBCs, platelets) - serotonin syndrome
26
Fluoroquinolone MOA
inhibits prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV ==> inhibition of DNA synthesis ex: levofloxacin
27
Fluoroquinolone side effects
- tendonitis/tendon rupture - QT prolongation - drug-drug interactions with divalent cations - **teratogenicity**
28
Folic acid synthesis inhibitors MOA
- Trimethoprim: inhibits bacterial dihydrofolate reductase - Sulfonamides (Sulfamethoxazole): inhibits dihydropteroate synthase when used in combination, they act synergistically and are bactericidal, and also decrease the likelihood of bacteria developing resistance to either of the drugs - Dapsone inhibition of dihydrofolic acid synthesis via competitive inhibition of para-aminobenzoic acid (PABA) for dihydropteroate synthetase --> different structure from Sulfonamides, but similar MOA
29
Folic acid synthesis inhibitor side effects
Trimethoprim: - hyperkalemia (increased K+ levels) - bone marrow suppression Sulfonamides: - hypersensitivity reactions - hemolysis if G-6-PD deficient - Steven-Johnson syndrome (bad skin disorder) - photosensitivity
30
Daptomycin MOA
binds to cytoplasmic membrane ==> creates transmembrane channels ==> depolarizes cell used for MRSA, vancomycin-resistant *Enterococcus* (VRE)
31
Daptomycin side effects
- myopathy - rhabdomyolysis - inactivated by pulmonary surfactant (cannot be used in pneumonia cases)
32
Polymyxin MOA
cationic polypeptides bind to cell membrane (detergent-like) ==> disrupt cell membrane ==> bacterial cell death used for very drug-resistant gram-negative rod infections ## Footnote "Polymyxins nix your nephrons and neurons"
33
Polymyxin side effects
- nephrotoxic - neurotoxic
34
Treatments for MRSA
Very Deadly Like Children Die Too - Vancomycin - Daptomycin - Linezolid - Clindamycin - Doxycycline - TMP-SMX
35
Treatments for VRE
- Linezolid - Daptomycin
36
Treatments for ESBL bacteria
Extended-spectrum beta-lactamase bacteria: *E. coli, Klebsiella* Tx: carbapenems (imipenem-cilastatin)
37
Anti-tubercular drugs (anti-TB drugs)
RIPE: - Rifampin - Isoniazid - Pyrazinamide - Ethambutol General treatment: 4 drugs for 2mo, then just Rifampin and Isoniazid for 4mo = 6mo total Latent treatment: Rifampin for 4mo, Isoniazid (with Vit B6) for 9mo
38
Isoniazid MOA
inhibits mycolic acid synthesis
39
Isoniazid side effects
- hepatotoxicity - peripheral neuropathy due to vitamin B6 deficiency <- supplement pts with vit B6 to prevent neurotoxicity "INH: Injures Neurons and Hepatocytes"
40
Rifampin MOA
inhibits bacterial DNA-dependent **R**NA polymerase ==> **R**amps up cyt P450 ==> prevents mRNA synthesis **R**apid resistance if used alone
41
Rifampin side effects
- many drug interactions because Rifampin is a potent inducer of CYP450 system (drug metabolism pathway) - **R**ifampin causes **R**ed-orange discoloration of all body fluids
42
Pyrazinamide side effects
- hepatotoxicity - hyperuricemia
43
Ethambutol MOA
inhibits arabinosyltransferase ==> inhibits cell wall synthesis
44
Ethambutol side effects
- optic neuropathy - can cause red-green colorblindness and decreased visual acuity "EYEthambutol"
45
Dapsone
used for leprosy, non-TB mycobacteria, some parasitic infections MOA: - inhibits dihydropteroate synthase Side effects: - hemolysis in patients with G-6-PD deficiency - methemoglobinemia
46
Treatable viruses
- **Herpesviruses: HSV, CMV, VZV** - **Influenza A and B** - RSV - Papillomavirus - HIV - Hepatitis B and C Goal: minimize spread
47
Antivirals for HSV and VZV
- Acyclovir - Valacyclovir - Famciclovir
48
Acyclovir MOA
- guanosine analog - acyclovir ==> acyclovir monophosphate ==> acyclovir diphosphate ==> acyclovir triphosphate (active product) - **competitive inhibitor of Herpesvirus DNA polymerase**, stops lengthening of DNA strand
49
Acyclovir side effects
- wide range of uses - IV formulation side effects: crystalline nephropathy, acute renal failure - MOR: mutation of thymidine kinase
50
Valacyclovir and Famciclovir
- oral prodrugs (need to be converted to active form) - Valacyclovir ==> Acyclovir - Famciclovir ==> Penciclovir - better bioavailability than Acyclovir
51
Antivirals for CMV
- Ganciclovir - Valganciclovir - Cidofovir - Foscarnet - Letermovir these drugs also work to treat HSV and VZV, but are only used if pt is resistant to Acyclovir
52
Ganciclovir and Valganciclovir
Ganciclovir: - IV formulation only - side effects: bone marrow toxicity (neutropenia) <- due to DNA polymerase being targeted, dividing cells are affected - MOR: mutated viral protein kinase Valganciclovir: - prodrug of Ganciclovir - oral drug only
53
Cidofovir
- used for CMV, acyclovir-resistant HSV - nucleotide analog - direct inhibitor of DNA polymerase - already has phosphate on it, so does not require viral kinase phosphorylation; can be used when there is a mutation in the viral thymidine kinase - MOR: mutated cellular kinase - side effects: nephrotoxicity
54
Foscarnet
- used for ganciclovir-resistant CMV or acyclovir-resistant HSV - pyrophophate analog - inhibition of DNA polymerase via binding to pyrophosphate binding-site - does not require any kinase activation - side effects: nephrotoxicity - MOR: mutated viral DNA polymerase "Foscarnet = pyro"fos"phate analog"
55
Antivirals for Influenza A & B
inhibition of influenza neuramindase ("N"): - Zanamavir: inhaled, contraindicated in asthma - Oseltamivir: oral - Baloxavir: new drug
56
Antiviral for RSV
Ribavirin: - inhibits RNA-dependent RNA polymerase - side effects: dose-related hemolytic anemia, teratogenic Palivizumab: - targets F glycoprotein on RSV surface - used for prevention of RSV in high-risk infants and children
57
Antifungals
- Polyenes (Amphotericin B, Nystatin) - Azoles ("-azole") - Echinocandins ("-fungin") - 5-Fluorocytosine - Allylamines (Terbinafine) - Griseofulvin
58
Amphotericin B
- binds to ergosterol - used for serious, systemic mycoses: Cryptococcus, Blastomyces, Coccidioides, Histoplasma, Candida, Mucor - side effects: fever/chills ("shake and bake"), hypotension, kidney dysfunction - side effects due to drug binding to cholesterol "Ampho**ter**icin '**tears**' holes in the fungal membrane by forming pores." ## Footnote amphibians have fungi? amphotericin B
59
Nystatin
- same mechanism as Amphotericin B: binds to ergosterol, forming pores in membrane - topical use only
60
5-Fluorocytosine (Flucytosine)
- inhibits DNA and RNA biosynthesis by conversion to 5-fluorouracil - used for systemic fungal infections **in combination with Amphotericin B**: Cryptococcus meningitis - side effects: bone marrow suppression
61
Azoles
- inhibits fungal sterol (ergosterol) synthesis by inhibiting cyt P-450 enzyme - used for local/less serious systemic mycoses - relatively friendly drug
62
Allylamines (Terbinafine)
- inhibits squalene epoxidase (early ergosterol synthesis) - used for dermatophytoses (**onychomycosis**, nail infections) - side effects: GI upset
63
Echinocandins
- "-fungin": Anidulafungin, caspofungin, micafungin - inhibits cell wall synthesis (beta-glucan) - used for Candida - side effects: GI upset "Echino**cand**ins work against **Cand**ida"
64
Griseofulvin
- disrupts mitosis by interfering with microtubule function - used for dermatophytes (tinea, ringworm) - side effects: teratogenic, carcinogenic
65
Antiprotozoa
Metronidazole: - G - Giardia - E - Entamoeba - T - Trichomonas "The METRO: GET out of his way!"
66
Metronidazole side effects
- disulfiram-like reaction when taken with alcohol: flushing, tachycardia, hypotension, abdominal pain, vomiting - metallic taste
67
Antiparasitics
**Albendazole/Mebendazole**: - pinworm ("worms are *bend*y") - MOA: microtubule inhibitors **Ivermectin**: - Strongyloides - MOA: paralyzes parasite by enhancing GABA transmission and cell hyperpolarization **Primaquine**: - liver hypnozoite stage of Plasmodium vivax/ovale - side effects: hemolytic crisis in those with G-6-PD deficiency **Chloroquine**: - sensitive malaria
68
Antimalarials
**Chloroquine**: - sensitive spp - blood stage (schizont) **Mefloquine**: - resistant spp - blood stage (schizont) **Atovaquone/Proguanil**: - resistant spp - liver schizont **Quinidine** or **Artestunate**: - life-threatening infection - blood stage (schizont) - side effects: cinchonism, long QT syndrome **Primaquine**: - P vivax and P ovale - liver hypnozoite stage - hemolytic anemia in patients with G-6-PD deficiency

Block 2 (11 decks)

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