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Medical Microbiology (Subject) / Antimicrobial DRUGS (Lesson)

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• Broad Band Antibiotic target a diverse group of MO
• Narrow Band Antibiotic few specific targets
• Reserve Antibiotics Specific situations Last Stand
• Bacteriostatic Stops MO growth
• Bacteriocidal kills MO
• Bacteriolytic kills AND lyses MO
• Minimal inhibitory concentration lowest concentration stopping growth
• minimal bactericidal concentration first well without any bacterial growth
• Bacetriolytic: Cycloserine inhibits racemization of L- and D- alanin inhibits formation of D-alanyl-D-alanin dipeptides NO CROSSLINKING IN CELL WALL BACTERIOLYTIC
• Bacitracin interferes with dephosphorylation of undecraprenyl pyrophosphat no peptidoglycan synthesis bacteriolytic
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• Vancomycin like penicillin glycopeptide blocks D-alanyl-D-alanin cap -->no crosslink MRSA started using lactate as cap ---> Abio cannot bind ---> crosslink possible
• beta-lactam-antibiotics irreversible inhibiton of transpeptidase beta-lactam ring resembles D-alanyl-D-alanin end => crosslinking inhibited
• beta-lactam: Penicillin (natural) pentacyclic ring works vs Strepto & Staphylococci susceptible to peniscillinases (cuts ring open)
• beta-lactam: Penicillin (semisynthetic) works also against gram negative Ampicillin (extended spectrum) Oxacillin (resistant to peniscillinase)
• beta-lactam: Xephalosporin hexaclyclic ring => resistant against penicillinase effective against Gram + and Gram -
• beta-lactam: Resistances beta-lactamases: cleave ring Some G(-): Porins don't let antibiotic in S.aureus has mutated a novel penicillin binding protein (transpeptidase),which has a low affinity to beta-lactam antibiotics
• Mycobacterium antibiotics Isoniazid INH: blocks reductase in mycolic acid biosynthesis Ethambuol: interferes with arabinogalactam biosynth. (which links peptidoglycane and mycolic acid) [Blocks conversion of glucose into mannose and arabinose]
• Protein synth: Erythromycin blocks movement of ribosome along mRNA Specific to 70S ribosomes (but mitochondria have similar ribosomes!)
• Streptomycin (aminoglycoside Abio) also Kanamycin, Gentamycin, Neomycin bind irreversible to 16S(of 30S unit) rRNA --> no initation --> misreading occur needs no oxygen (also works in necrotic tissue) Tuberculosis
• Tetracylcines Tetracyclin, Minocycline, Doxicyclin bind to 30s subunit (no prot synth) bacteriostatic used against intracellular bacteria resistances: multi drug eflux pump
• Spectinomycin bacteriostatic mRNA interaction with 30s blocked (but reversible) used vs Neisseria Gonorrhoea (penicillin resistant)
• 50s: Chloramphenicol inhibition of peptidyl transferase enzymatic inactivation by acetylation
• 50s: Oxazolidinone blocks binding of 50s to 30s used vs G(+) and MRSA
• Macrolides(erythromycin) Erythromycin, Spiramycin, Chlorathromycil inhibit ribosome translocation(movement) Spectrum: G(+), mycobacterium, legionella Resistance: binding site changed by enzyme
• Fusidic Acid elongation factor G locked to GDP => no energy G(+) cocci
• Antifungal: Azoles (triazoles) Inhibition of ergosterol synthesis
• Echinocandins inhibits beta glycane synth weakened cell wall LYSIS of cell
• Antifungal: Flucytosine antifungal Desamination desaminase (only in fungi) synth of proteins blocked
• Rifampin binds to DNA dependent RNA polymerase Target: Mycobacterium tuberculosis
• Quinolones Ciprofoxacin binds to DNA gyrase (topoisomerase) prevents supercoiling of DNA G(+)cocci Resistance: Eflux pump
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• Vitamins as Targets: Sulfonamides folic acid (vitamin B) synthesis stopped (1) Sulfomethexazole + (2) Trimethrophrim (1) blocks Dihydrofolic acid (2) blocks Tetrahydrofolic acid
• Antifungal:Polyenes Antifungal Amphitericin, Nystatin  form pores with ergosterol in cell membrane (fungi have ergosterol instead of cholesterol)
• Antiviral: Acyclovir Nucleoside analogue viral thymidin kinase --> acyclovir triphosphate --> DNA polymerization blocked infected cells killed therapy for HERPES
• Antiviral: Nucleoside analogs 3 prime missing blocks reverse transcription human DNA poly to picky
• Antiviral: non nucleoside analogues blocks reverse transcriptase itself shape changed
• Antiviral: Protease inhibitors no viral proteins produced viral proteins NEED CLEAVING
• Antiviral: Neuraminidase inhibitors Tamiflu neuraminidase needed to leave cell (attachement to membrane not cleaved) vs Influenza
• VS cell wall synthesis beta-lactam / Vancomycin / Cycloserine

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