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IMCB_Notes_Chapter 12

IMCB_Notes_Chapter 12 - Chapter 12 Antimicrobial drugs are...

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Chapter 12 Antimicrobial drugs are: Chemical substances used for treatment of infectious diseases – chemotherapy Antimicrobial drugs have selective toxicity (harmful against microbes and not the host) Antibiotic – substance produced by one microorganism that is inhibitory or toxic against other microorganisms the first discovered antibiotic was penicillin – Alexander Fleming in 1928 Mold – Penicillium notatum Its commercial use started in 1945 New antibiotics are being discovered by screening large number of microbes (400,000 screened; 3 useful drugs) Spectrum of Antibacterial Activity An antibiotic can be effective against a - narrow group of microbes (penicillin G – against Gram positive bacteria) - broad-spectrum antibiotic - disadvantage – eliminates also the normal micro flora Action of antimicrobial drugs Bactericidal – kill the microbe Bacteriostatic – inhibits the microbe Modes of antimicrobial action: Inhibition of - cell wall synthesis Inhibitors of cell wall synthesis Penicillins and cephalosporins interfere with the formation of peptidoglycan layer in the cell wall of bacteria (not present in eukaryotic cells). Bactericidal Penicillins/Cephalosporins These drugs block the enzymes that cross-link N-acetyl glucosamin and N-acetyl muramic acid Less effective Gr. negative bacteria – do not penetrate the outer membrane Penicillins Natural penicillin ( Penicillin G) It has a narrow spectrum (staphylococci, streptococci, and spirochetes) It is rapidly excreted from the body More efficient when injected than when taken orally It is susceptible to penicillinases (enzymes that cleave the penicillin molecule) Semisynthetic penicillins
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Partially produced by the mold Penecillum and partially by a chemical process The change of the shape of the molecule makes it more difficult to break up by
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IMCB_Notes_Chapter 12 - Chapter 12 Antimicrobial drugs are...

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