医学课件_《医用基础药理学》

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1、CHAPTER35ANTIBIOTICSJihongYaoIntroductionPharmacologicaleffects,Clinicaluses,untowardeffectofPenicillinG;PharmacolgicaleffectsofbroadspectrumPenicillinsandpenicillinase-resistantPenicillins;Spectrumofactivity,clinicaluseanduntowardeffectsofcephalosporins;Pharmacologicaleffects

2、andclinicaluseoferythromycin;Spectrumofactivity,clinicaluseanduntowardeffectsofAminoglycosides,TetracyclinesandChloramphenicols.Whatisantibiotics?Antibioticsaresolublecompoundsthatarederivedfromcertainmicroorganismsandthatinhibitthegrowthofothermicroorganisms.Beta-lactamantibio

3、tics(Beta内酰胺类抗生素)Beta-lactamantibioticscontainaBeta-lactamringinstructurewhichincludepenicillinsandcephalosporins.ThepenicillinsandcephalosporinsdifferinthatThenucleusofpenicillins6-aminopenicillanicacid(6-APA,6-氨基青霉烷酸)Thenucleusofcephalosporins7-aminocephalosporanicacid(7-ACA,

4、7-氨基头孢烷酸).StructureofpenicillinsandproductsoftheirenzymatichydrolysisPenicillinG(青霉素G)SpectrumofactivityofpenicillinGThepenicillin-susceptibleorganismsarenonpenicillinase-producingstrainsofmostgram-positiveandgram-negativecocci,gram-positivebacilli,andspirochetes.Mechanismofact

5、ionofpenicillinGPenicillinsinhibittheformationofcellwallandarebactericidalinaction.Penicillinexertsitseffectbybindingtocellularreceptorsnowidentifiedastranspeptidationenzymeswhichcatalyzedthecross-linkingreactionofcellwall.Bybindingtoandinhibitingtranspeptidationreactions,itint

6、erruptsthesynthesisofcellwallpeptidoglycan.Adefectivecellwallallowswatertoenterandswellthecell,causingmembranelysisandcelldeath.NotesTheactiondoesnotoccurredinmanoranimalswhodonotpossesthecellwallsurroundingthecellmembrane.Sincepenicillinspreventnewcross-linksduringtheformation

7、ofcellwallsanddonotdisruptestablishedcross-links,theyinterfereonlywithgrowingnotrestingcells.Penicillininsensitivebacteriahavestructurallydifferentcellwalls(containlesspeptidoglycan)suchasgram-negativebacilli.BacterialresistanceofPenicillinGPenicillinaseisabeta-lactamasewhichhy

8、drolyzesthebeta-lactamringofpenicillintoformpenicilloi