Antibiotic classes Flashcards
Give examples of aminoglycosides?
E.g. Gentamycin, Neomycin, Amikacin, Tobramycin, Streptomycin
Describe the MAO of aminoglycosides?
Bactericidal; irreversible inhibition of initiation complex through binding of 30S subunit -> misreading of mRNA. Also block translocation.
When are aminoglycosides indicated?
Gram-neg rod (e.g. E. coli, Klebsiella, Pseudamonas aeruginosa).
Aerobic bacteria
Ineffective against anaerobes (require O2 for uptake)
What is the MAO of penicillin?
Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes
When is penicillin indicated?
- Mostly gram pos organisms (e.g. S pneumonia, S pyogenes, Actinomyces)
- Gram neg cocci (N meningitides)
Spirochetes (T pallidum) - Penicillinase sensitive
Give examples of penicillinase-sensitive penicillin?
E.g. Amoxicillin, ampicillin, aminopenicillin
When is penicillinase-sensitive penicillin indicated?
Extended-spectrum penicillin (e.g. H influenzae, H pylori, E coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella, enterococci)
Describe the MAO of penicillinase-sensitive penicillin?
Block peptidoglycan cross-linking in cell wall.
Wider spectrum. Penicillinase sensitive.
Combine with clauvanic acid to protect against destruction by B-lactamase.
Give examples of penicillinase-resistant penicillins?
E.g. Dicloxacillin, Nafcilin, Oxacillin
When are penicillinase-resistant penicillins indicated?
S aureus (except MRSA)
Describe the MAO of penicillinase-resistant penicillins?
Block peptidoglycan cross-linking in cell wall.
Narrow spectrum.
Penicillinase resistance because bulky R group blocks access of B-lactamase to B-lactam ring.
Give examples of B-lactamase inhibitors?
e.g. (mnemonic CAST)
Clauvanic acid, sulbactam, Tazobactam
When are B-lactamase inhibitors indicated?
Often added to penicillin antibiotics to protect antibiotic from destruction by B-lactamase (Penicillinase)
Desribe the MAO of cephalosporins?
B lactam drugs that inhibit cell wall synthesis but are less susceptible to penicillinases. Bactericidal
Give examples and indications for 1st generation cephalosporins?
1st generation (e.g. Cefazolin, cephalexin) • Gram pos cocci (e.g. Staph aureus), gram neg rods (PEcK- Proteus mirabilis, E coli, Klebsiella pneumonia)
Give examples and indications for 2nd generation cephalosporins?
2nd generation (e.g. Cefaclor, Cefoxitin, Cefuroxime)
• Gram pos cocci (Staph, Strep, enterococcus)
• Gram neg (HENS PEcK- H influenzae, Enterobacter, Nisseria spp, Serratia, Proteus, E coli, Klebsiella)
Give examples and indications for 3rd generation cephalosporins?
3rd generation (e.g. ceftriaxone, cefotaxime, Ceftazidime • Serious gram neg infections resistant to other B lactams
Give examples and indications for 4th generation cephalosporins?
4th generation (e.g. cefepime) • Gram neg organisms (increased activity against Pseudomonas) • Gram pos organisms
Give examples and indications for 5th generation cephalosporins?
5th generation (e.g. ceftaroline) • Broad gram pos and neg coverage, including MRSA • Does NOT cover pseudomonas
Give examples of Carbapenems?
Imipenem, meropenem, ertapenem, doripenem
Describe the MAO of Carbapenems?
Imipenem is a broad-spectrum, β-lactamase– resistant carbapenem.
Always administered with cilastatin (inhibitor of renal dehydropeptidase I) to decrease inactivation of drug in renal tubules.
When are carbapenems indicated?
Gram ⊕ cocci, gram ⊝ rods, and anaerobes
Wide spectrum, but significant side effects limit use to life-threatening infections or after other drugs have failed.
Give an example of a Monobactam?
Aztreonam
What is the MAO of Monobactams?
Less susceptible to β-lactamases.
Prevents peptidoglycan cross-linking by binding to penicillin- binding protein 3. Synergistic with aminoglycosides.
No cross-allergenicity with penicillins.
What are Monobactams prescribed?
For penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides.
Gram ⊝ rods only—no activity against gram ⊕ rods or anaerobes.
Describe the MAO of vancomycin?
Inhibits cell wall peptidoglycan formation by binding D-ala D-ala portion of cell wall precursors. Bactericidal against most bacteria (bacteriostatic against C difficile).
Not susceptible to β-lactamases.
When should vancomycin be prescribed?
Gram ⊕ bugs only—serious, multidrug-resistant organisms, including MRSA, S epidermidis, sensitive Enterococcus species, and Clostridium difficile (oral dose for pseudomembranous colitis).
Give examples of Tetracylcines?
Tetracycline, doxycycline, minocycline
Describe the MAO of tetracyclines?
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.
Note: Do not take tetracyclines with milk (Ca2+), antacids (Ca2+ or Mg2+), or iron-containing preparations because divalent cations inhibit drugs’ absorption in the gut.
When are tetracyclines indicated?
Borrelia burgdorferi, M pneumoniae, Rickettsia, Chlamydia, acne
Describe the MAO of chloramphenicol?
Blocks peptidyltransferase at 50S ribosomal subunit.
Bacteriostatic.
When is chloramphenicol indicated?
Meningitis (Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae) and Rocky Mountain spotted fever (Rickettsia rickettsii).
Describe the MAO of clindamycin?
Blocks peptide transfer (translocation) at 50S ribosomal subunit. Bacteriostatic.
When is clindamycin indicated?
Anaerobic infections (eg, Bacteroides spp., Clostridium perfringens) in aspiration pneumonia, lung abscesses, and oral infections. - Treats anaerobic infections above the diaphragm vs metronidazole (anaerobic infections below diaphragm).
Also effective against invasive group A streptococcal infection.
Name some macrolides?
Azithromycin, clarithromycin, erythromycin.
Describe the MAO of macrolides?
Inhibit protein synthesis by blocking translocation (“macroslides”); bind to the 23S rRNA of the 50S ribosomal subunit. Bacteriostatic.
When are macrolides indicated?
Atypical pneumonias (Mycoplasma, Chlamydia, Legionella), STIs (Chlamydia), gram ⊕ cocci (streptococcal infections in patients allergic to penicillin), and B pertussis.
What are some SE of macrolide use?
MACRO: M- gastrointestinal Motility issues A- Arrhythmia caused by prolonged QT interval C- acute Cholestatic hepatitis R- Rash O- eOsinophilia
Name some sulfonamides?
Sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine.
Describe the MAO of sulfonamides?
Inhibit dihydropteroate synthase, thus inhibiting folate synthesis.
Bacteriostatic (bactericidal when combined with trimethoprim).
When are sulfonamides indicated?
Gram-⊕, gram ⊝, Nocardia, Chlamydia.
Sulfamethoxazole for simple UTI.
What is the mechanism of action of trimethoprim?
Inhibits bacterial dihydrofolate reductase.
Bacteriostatic.
When is trimethoprim indicated?
Used in combination with sulfonamides -> sequential block of folate synthesis.
Combination used for UTIs, Shigella, Salmonella, Pneumocystis jirovecii pneumonia treatment and prophylaxis, toxoplasmosis prophylaxis.
Name some flouroquinolones?
Ciprofloxacin, norfloxacin, levofloxacin, ofloxacin, moxifloxacin, gemifloxacin, enoxacin
Describe the MAO of flouroquinolones?
Inhibit prokaryotic enzymes topoisomerase
II (DNA gyrase) and topoisomerase IV.
Bactericidal.
Note: Must not be taken with antacids.
When are flouroquinolones indicated?
Gram ⊝ rods of urinary and GI tracts (including Pseudomonas), Neisseria, some gram ⊕ organisms.
Describe the MAO of metronidazole?
Forms toxic free radical metabolites in the bacterial cell that damage DNA.
Bactericidal, antiprotozoal.
When is metronidazole indicated?
("GET GAP" mnemonic)
G- Giardia
E- Entamoeba
T- Trichomonas
G- Gardnerella vaginalis,
A- Anaerobes (Bacteroides, C difficile)
P- H. Pylori
