10: Intro to Antimicrobials Flashcards
1
Q
What are antimicrobials?
A
- Drugs that destroy microbes, prevent their multiplication/growth, or prevent their action.
- Differ in physical/chemical/pharma properties
- Differ in spectrum of activity
- Differ in mechanism of action
2
Q
Name the different mechanisms of action.
A
- Inhibit cell wall synthesis
- Inhibit protein synthesis
- Alter nucleic acid metabolism
- Inhibit folate metabolism (needed to produce DNA, other metabolites)
- Other (e.g., disrupt cell membrane, produce free radicals)
3
Q
Name the antibiotics which inhibit cell wall synthesis.
A
- Penicillins (BL)
- Cephalosporins (BL)
- Monobactams [aztreonam] (BL)
- Carbapenems (BL)
- Glycopeptides [vancomycin]
- Lipoglycopeptide [televancin]
4
Q
Name the antibiotics which inhibit protein synthesis.
A
- Aminoglycosides
- Tetracylcines
- Glycylcycline [tigecycline]
- Macrolides/Azalides [azithromycin, clarithromycin]
- Lincosamides [clindamycin]
- Streptogramins [quinupristin/dalfopristin]
- Oxazolidinones [linezolid]
- Chloramphenicol
“All true germs must like stinky old cheese”
5
Q
Name the antibiotics which alter nucleic acid metabolism.
A
- Rifamycins [Rifampin]
- Quinolones
6
Q
Name the antibiotics which inhibit folate metabolism.
A
- Trimethoprim
- Sulfonamides
7
Q
Name the miscellaneous antibiotics.
A
- Metronidazole
- Lipopeptides [daptomycin]
- Polymyxins
8
Q
List the uses of the various beta-lactam antibiotics.
A
- Penicillin: GAS, syphilis
- 1GC: cephalexin for soft tissue infection by sensitive S. aureus
- 3GC: ceftriaxone for meningitis or pneumonia due to S. pneumoniae
- Monobactam (aztreonam): serious GN infx (pseudomonas) in penicillin-allergic pt.
- Semi-synthetic anti-staph penicillin: oxacillin for serious, sensitive S. aureus infx (MSSA)
- Anti-pseudomonal penicillin/beta-lactamase inhibitor: piperacillin/tazobactam for broad-spectrum coverage of serious infection, including GP, GN (pseudomonal coverage), anaerobes
- Carbapenem: meropenem: broad-spectrum coverage for serious infx, suspect abx resistance, covers pseudomonas
9
Q
Identify where the protein synthesis inhibitors act.
A
- 30S: aminoglycosides, tetracyclines
- 50S: streptogramins, macrolides, chloramphenicol, lincosamides, oxazolidinones
10
Q
List the uses of the various protein synthesis inhibitors.
A
- Aminoglycosides: tobramycin used w/ other abx to treat pseudomonas
- Tetracyclines: acne, doxycycline (lyme disease except kids –> amoxacillin)
- Macrolides: azithromycin for outpatient pneumonia
- Lincosamides: clindamycin to treat oral abscess (GP, anaerobe coverage)
- Oxazolidinones (linezolid): treat MRSA, given orally
11
Q
Describe the mechanism/indication for rifamycins.
A
- Rifampin (rifampicin)
- Blocks mRNA synthesis by binding bacterial DNA-dependent RNA polymerase
- Resistance via single-step mutation
- Use rifampin in combination with other abx (except as prophylaxis for N. meningitidis)
- Use in treatment of TB
12
Q
Describe the mechanism/indication for quinolones.
A
- Inhibit DNA synthesis and cause cell death; inhibit topoisomerases responsible for supercoiling DNA (DNA gyrase) or relaxing supercoiled DNA (topoisomerase IV)
- Ciprofloxacin for anthrax (others include levofloxacin, moxifloxacin)
- Use for CAP (levofloxacin)
13
Q
Describe the mechanism/indication for inhibitors of folate metabolism.
A
- Trimethoprim and sulfonamides
- Inhibiting folate metabolism means formation of DNA precursors is reduced, and DNA synthesis inhibited
- Give in combination (e.g., trimethoprim-sulfamethoxazole [TMP-SMZ])
- Indications: Pneumocystis jirovecii (PCP) prophylaxis (AIDS pts), staph skin infx, E. Coli UTIs
14
Q
Describe the mechanism/indication for metronidazole.
A
- Active against aerobes like Clostridium difficile (causes colitis) and parasites such as entamoeba, trichomonas, giardia
- Diffuses into cell and reduced; free radicals cause breakage of organism DNA, leading to cell death
15
Q
Describe the mechanism/indication for daptomycin (lipopeptide).
A
- Only abx in lipopetide class
- Binds cell membrane of GP in calcium-dependent process –> depolarization, disrupted cell membrane processes, halted RNA/DNA/protein synthesis –> cell death
- Indications: resistant staph (e.g., MRSA) and enterococcal infx
- Cannot be used for pulmonary infections (bound by surfactant)
