感染的治疗（英文）Treatmentof .ppt

Treatment of Infection Professor Mark Pallen Treatment of Infection How Do Antimicrobials Work? Key concept: selective toxicity the antimicrobial agent blocks or inhibits a metabolic pathway in a micro-organism which is either absent or is radically different in the mammalian cells of the human host Principle of antibiotic spectrum Different antibiotics target different kinds of bacteria i.e., different spectrum of activity Examples: Penicillin G (= original pen.) mainly streptococci (narrow spectrum) Vancomycin only Gram-positive bacteria (intermediate spectrum) Carbapenems many different bacteria (very broad spectrum) Treatment of Infection Anti-Microbial Drug Targets Antimicrobials acting on the bacterial cell wall Interfere with synthesis of peptidoglycan layer in cell wall eventually cause cell lysis bind to and inhibit activity of enzymes responsible for peptidoglycan synthesis aka “penicillin-binding proteins” Antimicrobials acting on the bacterial cell wall Beta-lactams: Penicillins benzylpenicillin flucloxacillin ampicillin piperacillin Antimicrobials acting on the bacterial cell wall Beta-lactams: Cephalosporins Orally active cephradine cephalexin Broad spectrum cefuroxime cefotaxme ceftriaxone ceftazidime Antimicrobials acting on the bacterial cell wall Unusual beta-lactams Carbapenems Imipenem, meropenem very wide spectrum Monobactams Aztreonam only Gram-negatives Glycopeptides only Gram-positives, but broad spectrum vancomycin teicoplanin Antimicrobials acting on nucleic acid synthesis  Inhibitors Of Precursor Synthesis sulphonamides trimethoprim are synthetic, bacteriostatic agents used in combination in co-trimoxazole Sulphonamides inhibit early stages of folate synthesis dapsone, an anti-leprosy drug, acts this way too Trimethoprim inhibits final enzyme in pathway, dihydrofolate synthetase. pyramethamine, an anti-toxoplasma and anti-PCP drug acts this way too Antimicrobials acting on nucleic acid synthesis Inhibitors of DNA repl