Antibacterials Flashcards
Gram Negative Bacterial Cell Wall composition
LPS outer membrane (protects against some antibiotics)
thin peptidoglycan (5% of wall)
inner membrane
Narrow spectrum antibacterials
effective against either Gram + or Gram -, but not both
Broad spectrum antibacterials
effective against both Gram+ and Gram-
Opportunistic Infections
Infections that would not normally harm an immunocompetent person
can be from existing colonizing gut microflora become infectious due to immunocompromised state
Cell wall synthesis antibacterials (3)
Penicillins
cephalosporins
vancomycin
Protein synthesis antibacterials (3)
macrolides
tetracyclines
aminoglycosides
Transcription mechanism antibacterials (1)
Fluoroquinolones
Metabolic pathways antibacterials (2)
Sulfonamides
trimethoprim
Sulfonamides (2)
Mechanism:
Indications:
Contraindications:
Adverse effects:
Sulfamethoxazole (combined with trimethoprim, but sulf works earlier in the anabolic pathway)
Bacteriostatic, metabolite inhibitors
Broad spectrum
Mechanism: Prevent synthesis of folic acid (looks very similar to PABA which is important in the synthesis of folic acid)
Indications: Used for UTIs because they reach effective concentrations in the urinary tract
Contraindications: sulfa drug allergy (thiazide, loop diuretics), pregnant women (breastfeeding or infants)
Adverse effects: skin allergies (Stevens-Johnson, photosensitivity), bone marrow suppression (agranulocytosis, thrombocytopenia, and anemia), nausea vomiting
β-Lactam Antibacterials (3)
Penicillins
Cephalosporins
Carbapenems
(FYI only) Monobactams
Bactericidal - Inhibit cell wall enzyme responsible for peptidoglycan synthesis
Penicillins (several)
Mechanism:
Indications:
Contraindications:
Adverse effects:
β-lactam antibiotics come from a Penicillium mold
Natural are narrow spectrum against Gram+, sensitive to β-Lactamases (e.g., G and V)
Semi-synthetic are broad spectrum
Resistant to β-Lactamases - Cloxacillin
Broader spectrum - Aminopenicillins (amoxicillin PO, ampicillin not PO)
Extended spectrum - anti-pseudomonal penicillins (ticarcillin, piperacillin)
Mechanism: Bactericidal. Inhibit cell wall enzyme responsible for peptidoglycan synthesis. Use in combination with β-lactamase inhibitors (clavulanic acid)
Indications: Gram+ bacteria (and some Gram-)
Given PO, IM, IV
Penicillin G is IV or IM; Penicillin V is PO
Contraindications: Allergy to penicillin
Adverse effects: disturb normal gut flora, fatal allergic reactions (skin rashes, lip swelling)
Cephalosporins (1?)
First --> Fifth gen developments: Mechanism: Indications: Contraindications: Adverse effects:
Most widely used antibacterial drugs
β-lactam antibiotics come from a Cephalosporium fungus
First –> Fifth gen:
Cefazolin –> Cefuroxime –> Cefotaxime –> Cefepime –> Ceftaroline
(fa, fur, fo, fe, fta)
- Great against Gram+, IV
- Surgical prophylaxis, not anaerobes
- IV and IM, CSF/meninges infections
- Broader than 3rd gen esp Gram+
- MRSA infections
Mechanism: inhibits cell wall synthesis
Indications: Varies from 1st to 5th gen. Fifth gen better against Gram(-) and better β-lactamase resistance
Contraindications: penicillin allergy (but might still be used anyway)
Adverse Effects: Similar to pencillins
Carbapenems (1)
Mechanism:
Indications:
Contraindications:
Imipenem (given with cilastatin–inhibits breakdown of imipenem in kidney)
Mechanism: Broad spectrum. Inhibit cell wall synthesis. All given parenterally - not orally
Indications: Gram positive, negative, and anaerobic. Mixed infections
Contraindications: a “last resort” antibiotic, not used for MRSA, resistant bacteria (Enterobacteriaceae, Klebsiella pneumoniae)
Macrolides (3)
Mechanism:
Indications:
Contraindications:
Adverse effects:
Erythromycin
azithromycin
clarithromycin
Mechanism: Protein synthesis (binds to bacterial 50S ribosomes). Bacteriostatic and bactericidal
Indications: Infections of respiratory tract (Streptococcus pyogenes, Haemophilus influenzae), skin, and soft tissue. Syphilis, Lyme disease, Gonorrhea, Chlamydia, Mycoplasma. Patients allergic to β-lactamases-lactam, HIV/AIDS (azithromycin + clarithromycin)
Contraindications: compete for hepatic metabolism with other drugs (theophylline, warfarin, cyclosporine, digoxin)
Adverse effects: GI disturbances (hepatotoxicity)
Tetracyclines (1)
Mechanism:
Indications:
Contraindications:
Adverse effects:
Tetracycline
Mechanism: Bacteriostatic. Broad spectrum. Inhibit protein synthesis (30S ribosomal subunit)
Indications: Gram(-) and Gram(+). Mycoplasma, Rickettsia, Chlamydia, syphilis. Protozoa
Contraindications: Do not take with dairy. Binds to metal ions (Ca2+ , Mg2+, iron, aluminium) in milk products, supplements, some laxatives, most antacids. Will form insoluble complexes (chelation). Do not use in children less than 8 years old, Pregnancy/breast feeding. Discoloration of teeth
Adverse effects: GI disturbances, gut flora reduction. Superinfection by Candida. Pseudomembranous colitis (caused by Clostridium difficile). It potentiates warfarin.
Antagonistic to bactericidal antibiotics so must be timed for use usually at least an hour apart
