FA - Micro - Antimicrobials Flashcards
Antimicrobials - DNA topoisomerases?
Fluoroquinolones: 1. Ciprofloxacin 2. Levofloxacin Quinolone 1. Nalidixic acid
Antimicrobials - Folic acid synthesis (DNA methylation)?
Sulfonamides: 1. Sulfamethoxazole 2. Sulfisoxazole 3. Sulfadiazine \+ Trimethoprim.
Antimicrobials - Damages DNA?
Metronidazole
Antimicrobials - mRNA synthesis (RNA pol)?
Rifampin
Antimicrobials - Protein Synthesis - 50S subunit?
- Chloramphenicol
- Clindamycin
- Linezolid
Macrolides: - Azithromycin
- Clarithromycin
- Erythromycin
Streptogramins - Quinupristin
- Dalfopristin
Antimicrobials - Protein synthesis - 30S subunit?
Aminoglycosides 1. Gentamicin 2. Neomycin 3. Amikacin 4. Tobramycin 5. Streptomycin Tetracyclines: 1. Tetracycline 2. Doxycycline 3. Minocycline
Antimicrobials - Cell wall synthesis - Peptidoglycan synthesis - Glycopeptides?
- Vancomycin
2. Bacitracin
Antimicrobials - Peptidoglycan cross-linking - Penicillinase-sensitive penicillins?
- Penicillins G, V
- Ampicillin
- Amoxicillin
Antimicrobials - Cell wall synthesis - Peptidoglycan cross-linking - Penicillinase-resistant penicillins?
- Oxacillin
- Nafcillin
- Dicloxacillin
Antimicrobials - Cell wall synthesis - Peptidoglycan cross linking - Antipseudomonals?
- Ticarcillin
2. Piperacillin
Antimicrobials - Cell wall synthesis - peptidoglycan cross-linking Cephalosporins?
1st - Cephazolin 2nd - Cefoxitin 3rd - Ceftriaxone 4th - Cefipime 5th - Ceftaroline
Antimicrobials - Cell wall synthesis - Peptidoglycan cross-linking Carbapenems?
- Imipenem
- Meropenem
- Ertapenem
- Doripenem
Antimicrobials - Cell wall synthesis - Peptidoglycan cross-linking - monobactams?
Aztreonam
Penicillin G route?
IV, IM
Penicillin V route?
Oral
Penicillin G, V - Mechanism?
- Bind penicillin-binding proteins (transpeptidases)
- Block transpeptidase cross-linking of peptidoglycan.
- Activate autolytic enzymes.
Penicillin G, V - Clinical use?
- Mostly for Gram(+) - S.pneumoniae, S.pyogenes, Actinomyces.
- Also for N.meningitidis, T.pallidum.
- Bactericidal for gram(+) cocci, gram(+) rods, gram(-) cocci, spirochetes.
- Penicillinase sensitive.
Penicillin G,V - Toxicity?
- HSR
2. DIRECT COOMBS (+) Hemolytic anemia
Penicillin G, V - Resistance?
Penicillinase in bacteria (a type of beta-lactamase) cleaves beta-lactam ring.
Ampicillin, amoxicillin - Mechanism?
Same as penicillin. Wider spectrum + Penicillinase SENSITIVE.
–> Combine with clavulanic acid to protect against beta-lactamase.
Ampicillin vs Amoxicillin - Bioavailability?
Amoxil > Ampicillin
Ampicillin/Amoxicillin - Clinical use?
Extended-spectrum penicillin:
- H.influenza
- E.coli
- L.monocytogenes
- P.mirabilis
- Salmonella
- Shigella
- Enterococci
Ampicillin/Amoxicillin - Toxicity?
- HSR
- Rash
- Pseudomembranous colitis
Ampicillin/Amoxicillin - Mechanism of resistance?
Penicillinase in bacteria (a type of beta-lactamase) cleaves beta-lactam ring.
Oxacillin/Nafcillin/Dicloxacillin - Mechanism?
Same as penicillin. Narrow spectrum - Penicillinase-RESISTANT because bulky R group blocks access of beta-lactamase to beta-lactam ring.
Oxacillin/Nafcillin/Dicloxacillin - Clinical use?
S.aureus - except MRSA - resistant because of altered penicillin-binding protein target site.
Oxacillin/Nafcillin/Dicloxacillin - Toxicity?
- HSR
2. Interstitial nephritis
Ticarcillin/Piperacillin (antipseudomonals) - Mechanism?
Same as penicillin. Extended spectrum.
Ticarcillin/Piperacillin (antipseudomonals) - Clinical use?
- Pseudomonas spp.
- Gram(-) rods
- Susceptible to penicillinase
- Use with beta-lactamase inhibitors
Ticarcillin/Piperacillin (antipseudomonals) - Tox?
HSR
Mention beta-lactamase inhibitors?
- Clavulanic acid
- Sulbactam
- Tazobactam
Cephalosporins - Mechanism?
- Beta-lactam drugs that inhibit cell wall synthesis but are less susceptible to penicillinases.
- Bactericidal.
Organisms typically NOT covered by cephalosporins?
LAME:
Listeria
Atypicals (Chlamydia, Mycoplasma)
MRSA
Enterococci
Exception: Ceftaroline covers MRSA.
1st Gen cephalosporins - Clinical use?
Cefazolin, cephalexin.
- Gram(+) cocci
- P.mirabilis
- E.coli
- K.pneumoniae
- Cefazolin used prior to surgery to prevent S.aureus wound infections.
2nd gen cephalosporins - Clinical use?
Cefoxitin, cefaclor, cefuroxime:
- Gram(+) cocci
- H.influenza
- Enterobacter aerogenes
- Neisseria spp.
- P.mirabilis
- E.coli
- K.pneumoniae
- S.marcescens
3rd gen cephalosporins - Clinical use?
Ceftriaxone, cefotaxime, ceftazidime.
Serious gram(-) infections resistants to other beta-lactams.
Ceftriaxone –> Meningitis + Gonorrhoeae + Disseminated LYME.
Ceftazidime –> Pseudomonas.
4th gen cephalosporins - clinical use?
Cefepime.
Incr. activity against pseudomonas + gram(+) organisms.
5th gen cephalosporins - clinical use?
Ceftaroline. Broad gram(+) and gram(-) organism coverage, incl. MRSA. Does NOT cover Pseudomonas.
Cephalosporins toxicity?
- HSR.
- Autoimmune hemolytic anemia.
- Disulfiram-like reaction.
- VitK def.
- Low cross-reactivity with penicillins.
- Increase nephrotoxicity of aminoglycosides.
Aztreonam - Mechanism?
- Monobactam - resistant to beta-lactamases.
- Prevents peptidoglycan cross-linking by binding to penicillin-binding protein 3.
- Synergistic with aminoglycosides.
- No cross-allergenicity with penicillins.
Aztreonam - Clinical use?
- Gram(-) rods only.
- No activity against gram(+) or anaerobes.
- For penicillin allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides.
Aztreonam - toxicity?
Usually nontoxic - occasional GI upset.
Aminoglycosides - Mechanism?
- Bactericidal
- Inhibit formation of initiation complex and cause misreading of mRNA.
- Also block translocation.
- Require O2 for uptake - therefore ineffective against anaerobes.
Aminoglycosides - Clinical use?
- Severe gram(-) rods.
- Synergistic with beta-lactams
- Neomycin for bowel surgery.
Aminoglycosides toxicity?
- Nephrotoxicity (especially when used with cephalosporins)
- Neuromuscular blockade
- Ototoxicity (especially when used with loop diuretics)
- Teratogen
Aminoglycosides - Mechanism of resistance?
Bacterial transferase enzymes inactivate the drug by acetylation, phosphorylation, or adenylation.
Tetracyclines - mechanism?
- Bacteriostatic
- Bind to 30S and prevent attachment of aminoacyl-tRNA.
- Limited CNS penetration.
- Doxycycline is fecally eliminated and can be used in patients with renal failure.
- Do NOT take with milk (Ca), antacids (Ca, Mg), or iron-containing preparations because divalent cations inhibit its absorption in the gut.
Tetracyclines - Clinical use?
- Borrelia burgdorferi
- M.pneumoniae
- Drug’s ability to accumulate intracellularly makes it very effective against Rickettsia/Chlamydia.
- Also used to treat acne.
Tetracyclines - Toxicity?
- GI distress
- Discoloration of teeth and inhibition of bone growth in children
- Photosensitivity
- Contraindicated in pregnancy
Tetracyclines - Mechanism of resistance?
- Decr. UPTAKE
2. Incr. EFFLUX out of bacterial cells by plasmid-encoded transport pumps.
Macrolides - Mechanism?
- Inhibits protein synthesis by blocking TRANSLOCATION (macroslides).
- Bind to the 23S rRNA of the 50S subunit.
- Bacteriostatic.
Macrolides - Clinical use?
- Atypical pneumonias
- STDs (Chlamydia)
- Gram(+) cocci (strep infections in patients allergic to penicillin).
Macrolides - toxicity?
- GI motility issues
- Arrhythmia caused by prolonged QT
- Acute cholestatic hepatitis
- Rash
- Eosinophilia
- Incr. serum concentration of theophyllines + Oral anticoagulants.
- Erythro + Clarithro INHIBIT CYP450.
Macrolides - mechanism of resistance?
Methylation of 23S rRNA-binding site prevents binding of drug.
Chloramphenicol - Mechanism?
Blocks peptidyltransferase at 50S ribosomal subunit - Bacteriostatic.
Chloramphenicol - Clinical use?
- Meningitis (H.influenza, N.meningitidis, S.pneumoniae).
- RM spotted fever - R.rickettsii
- Limited use due to toxicity but often still in developing countries because of low cost.
Chloramphenicol - Toxicity?
- Anemia - DOSE-dependent.
- Aplastic anemia - DOSE-dependent.
- Gray baby syndrome - in premature infants because they lack liver UDP-glucuronyl transferase.
Chloramphenicol - Mechanism of resistance?
Plasmid-encoded acetyltransferase inactivates the drug.
Clindamycin - Mechanism?
Blocks peptide transfer (translocation) at 50S - Bacteriostatic.
Clindamycin - Clinical use?
- Anaerobic infections (e.g., Bacteroides spp., C.perfringens) in aspiration pneumonia, lung abscesses, oral infections.
- Also effective against invasive Group A strep infection.
Clindamycin vs Metronidazole?
Treats anaerobes ABOVE the diaphragm.
Clindamycin - toxicity?
- Pseudomembranous colitis (C.difficile overgrowth)
- Fever
- Diarrhea
Sulfonamides - Mechanism?
- Inhibit folate synthesis.
- Para-aminobenzoic acid (PABA)
- Antimetabolites inhibit dihydropteroate synthase.
- Bacteriostatic
Sulfonamides - Clinical use?
- Gram(+)
- Gram(-)
- Nocardia
- Chlamydia
- Triple sulfas or SMX for simple UTI
Sulfonamides - Toxicity?
- HSR
- Hemolysis if G6PD deficient
- Nephrotoxicity (tubulointerstitial nephritis)
- Photosensitivity
- Kernicterus in infants
- Displace other drugs from albumin (e.g., warfarin)
Mechanism of resistance - Sulfonamides?
- Altered enzyme (bacterial dihydropteroate synthase)
- Decr. UPTAKE
- Incr. PABA synthesis
Trimethoprim - mechanism?
Inhibits bacterial dihydrofolate REDUCTASE - Bacteriostatic.
Trimethoprim - Clinical use?
- Used in combination with sulfonamides (TMP-SMX)
- Cause sequential block of folate synthesis.
- Combination used for UTIs, Shigella, Salmonella, Pneumocystis jirovecii pneumonia treatment and prophylaxis.
- Toxo prophylaxis.
Trimethoprim - Toxicity?
- Megaloblastic anemia
- Leukopenia
- Granulocytopenia
May alleviate with supplemental folinic acid.
Fluoroquinolones - mechanism?
- Inhibits DNA gyrase (topoiso II) + topoiso IV.
- Bactericidal.
- Must not be taken with antacids.
Fluoroquinolones - Clinical use?
Gram(-) rods of urinary and GI tracts (including Pseudomonas), Neisseria, some gram(+) organisms.
Fluoroquinolones - Toxicity?
- GI upset
- Superinfections
- Skin rashes
- Headaches
- Dizziness
Fluoroquinolones - Less common toxicity?
- Tendonitis
- Tendon rupture
- Leg cramps
- Myalgias
- Contra in pregnancy, nursing mothers , and children under 18yrs due to possible damage to cartilage.
- May prolong QT syndrome
- May cause tendon rupture in people >60 and in patients taking prednisone.
Fluoroquinolones - Mechanism of resistance?
Chromosome-encoded mutation in DNA gyrase, plasmid-mediated resistance, efflux pumps.
Metronidazole - mechanism?
Forms free radical toxic metabolites in the bacterial cell that damages DNA. Bactericidal, antiprotozoal.
Metronidazole - Clinical use?
- Giardia
- Entamoeba
- Trichomonas
- G.vaginalis
- Anaerobes (bacteroides, C.difficile)
- H.pylori + clarithromycin + PPI
Metronidazole - Disulfiram-like toxicity?
- Disulfiram-like reaction - severe flushing, tachycardia, hypotension with alcohol.
- Headache
- Metallic taste
M.tuberculosis - prophylaxis?
Isoniazid
M.tuberculosis - Treatment?
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol (RIPE for treatment)
M.avium-intracellulare - Prophylaxis?
- Azithromycin
2. Rifabutin
M.avium-intracellulare - treatment?
- More drug resistant than M.tuberculosis.
- Azithromycin or clarithromycin + ethambutol
- Can add rifabutin or ciprofloxacin.
M.leprae - prophylaxis?
No prophylaxis.
M.leprae - Treatment?
- Long-term treatment with dapsone + rifampin for TUBERCULOID FORM.
- Add clofazimine for LEPROMATOUS form.
Isoniazid - Mechanism?
- Decr. synthesis of mycolic acids.
2. Bacterial catalase-peroxidase (encoded by katG) needed to convert INH to active metabolite.
Isoniazid - Clinical use?
M.tuberculosis - the ONLY agent used as solo prophylaxis against TB.
Isoniazid - fast vs slow acetylators?
Different half-lives.