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2016-02-19 19:05:08
Micro antibiotics
Micro Antibiotics
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  1. penicillin
    • beta lactam
    • cell wall synthesis inhibitor
    • binds PBPs transpeptidase which are regulatory enzymes for cross linking of peptidoglycan layers

    • Natural Penicillins: G / V: G+
    • Amino Penicillins: Amoxicillin / Ampicillin: Broad
    • Anti-Staph Penicillins (resistant to beta lactamase): Methicillin: not G-
    • Anti-pseudomonal Penicillins: Piperacillin: Broad (including G-)

    • Resistance
    • G-: beta lactamase
    • G+: modified PBP + inducible beta lactamase
  2. Cephalosporins/Cephalomycins
    • beta lactam
    • cell wall synthesis inhibitor
    • binds PBPs D alanyl Carboxy Peptidase

    • 1st Gen: Cephalexin / Cephradine: G+
    • 2nd Gen: Cefoxitin / Cefotetan: Anaerobes (G+ / G-)
    • 3rd Gen: Cefepime: G- (G+) : Risk of forming extended spectrum beta lactamases
    • 4th Gen: Cefclidine: Pseudomonas (Broad)
    • 5th Gen: Ceftobiprole: MRSA (G+ / G-)

    • Resistance
    • G-: beta lactamase
    • G+: modified PBP + inducible beta lactamase
  3. Carbapenems/Monobactams
    • immipenem / meropenem
    • beta lactam
    • cell wall synthesis inhibitor
    • binds PBPs and enzymes responsible for peptidoglycan synthesis

    • Everything except: MRSA / VRE / Pseudomonas / Mycoplasma
    • Reserve antibiotic (IV only)

    very stable against beta lactamases
  4. ß-lactams/ß-lactam inhibitors
    • binds to ß-lactamases of bacs and prevent enzymatic inactivation of ß-lactam
    • used in combination with normal beta lactam antibiotic
  5. Glycopeptides
    • Vancomycin
    • cell wall synthesis inhibitor
    • inhibits cross-linkage of peptidoglycan layers (D-ala - D-ala)

    inactive against G- (molecule can't pass outer membrane)

    • Intrinsic Resistence Enterococci: D-ala - D-ser instead of D-ala - D-ala
    • Plasmid mediated acquired resistance of Staph
  6. Daptomycin
    causes depolarization of cytoplasmic membrane --> resulting in disruption of ioni concentration gradients
  7. Polymyxins
    • Cell membrane inhibitor
    • inserted into bacterial membrane and causes increased cell permeability

    • G- bacili
    • G+ dont have outer membrane so not as effective
    • Topical usually
  8. isoniazid, Ehionamide
    • cell wall synthesis inhibitor
    • inhibit myocolic acid synthesis
    • bactericidal

    Mycobacetria  (antituberculotic!!)
  9. ethambutol
    inhibits arabinogalactan synthesis

    • actively replicating bacteria
    • antituberculotic!!
  10. cycloserine
    inhibits cross-linkage of petidoglycan layers
  11. Aminoglycosides
    • protein synthesis inhibitor
    • produce premature release of aberrant peptide chains from 30S ribosomes
    • Bactericidal
    • IV only

    • G- bacilli
    • Used only in serious infection, long term therapy and patients with renal failure
    • high toxicity

    • Resistance:
    • Decreased uptake via cell wall (need oxygen to pass cell membranes so anaerobes are resistant)
    • enzymatic modification of peptides of antibiotic
    • mutation of ribosomal binding site (Enterococci)
  12. Chloramphenicol
    • protein synthesis inhibitor
    • Binds to peptidyl Transferase on 50S ribosomal subunit

    • Broad Spectrum but only used for Typhoid fever
    • Crosses blood brain barrier
    • Toxicity: Irreversible aplastic anemia (affects human protein synthesis too)

    • Resistance:
    • acetyltransferase enzyme modifies chloramphenicol (plasmid)
    • mutation fo outer membrane porin protein (G-)
  13. Tetracyclines
    • protein synthesis inhibitor
    • prevent binding of tRNA at 30S ribosome
    • bacetreiostatic

    Broad Spectrum

    • Resistance: very common
    • decreased penetration into cell by mutation in outer membrane porin (G-)
    • active efflux - most common
    • altered target site
    • Chelates with mmilk etc. in diet so could pass through GIT without absorption
    • enzymatic modification of the antibiotic
  14. Oxazolidinons
    • Protein synthesis inhibitor
    • Linezolid
    • prevents initiation of protein synthesis at 50S ribosome

    Reserved for multidrug resistant strains

    • Resistance:
    • no cross resistance because it is a unique mechanism
  15. Macrolide
    • Protein synthesis inhibitor
    • prevent polypeptide elongation at 50S ribosomal subunit
    • Bacteriostatic

    Absorbed better in G+

    • Resistance:
    • Methylation of 50S ribosomal subunit
    • erythromycin esterase
  16. Lincosamide
    • protein synthesis inhibitor
    • Clindamycin
    • prevents polypeptide elongation at 50S ribosomal subunit

    • Anaerobic G- bacilli
    • G+ cocci (staph)

    • Resistance:
    • Inducible methylation of 50S ribosomal subunit (cross resistance)
  17. Quinolones
    • Nucleic acid synthesis inhibitor
    • Binds alpha subunit of DNA gyrase
    • Bactericidal

    • 1st Gen: G-
    • 2nd Gen: Broad
    • 3rd Gen: G+ and Anaerobes
    • Popular because it si cheap, has high tissue distribution and can be taken orally

    • Resistance:
    • changes in porin proteins (G-)
    • efflux pumps (unable to affect intracellular bacteria)
    • inhibiting proteins
  18. Rifampin,Rifabutin
    • nucleic acid synthesis inhibitor
    • prevent transcription by binding DNA-dep. RNA polymerase

    • Antituberculotic!!
    • G+ cocci
    • Hepatotoxic

    • Resistance: develops fast
    • mutation of beta subunit of RNA polymerase (G+)
    • unable to be taken up by G-
  19. Metronidazole
    • nucleic acid synthesis inhibitor
    • disrupts DNA of bacs (is a cytotoxic compound)
  20. Co-trimoxazole
    • anti-metabolite
    • Sulfonamide
    • inhibits dihydropteroate synthase and disrupts folic acid synthesis (B9)


    • Resistance:
    • decreased affinity
    • natural resistance if use thymidine as external source of B0 (enterococci)
  21. Trimethoprim
    • Anti-metabolite
    • inhibits dihydrofolate reductase and disrupts folic acid synthesis