18. Beta Lactams - -Lactam Antibiotics There is no such...

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β -Lactam Antibiotics There is no such thing as an antibiotic that works against all bacteria– therefore knowing which agents will treat which bacteria (coverage) is crucial. Penicillins • Natural penicillins: – Penicillin G: widely used, inactivated by β - lactamases (penicillinases), given orally, i.v., topically, i.m. – Penicillin V: less active than G, favored for some oral infections, more acid - stable, given orally • Penicillinase-resistant penicillins: – methicillin (MRSA) – cloxacillin Penicillins II • Aminopenicillins: – ampicillin (active against entrococcal) – amoxicillin (better gram negative spectrum) • Extended spectrum penicillins: – piperacillin (active against entrococcal) • Penicillin/Pencillinase inhibitor combinations: – amoxicillin + clavulanic acid β -Lactam Mechanism of Action • Bind to penicillin-binding proteins (PBPs) • Inhibit bacterial cell wall (peptidoglycan) synthesis leading to a defective cell wall • Induce bacterial autolytic enzymes (autolysins) leading to cell lysis • They are generally bactericidal (good) rather than bacteriostatic (less good) β -Lactam Mechanism of Resistance • Altered membrane permeability to β - lactams • Alteration of the structure of penicillin binding proteins (PBPs) • Inactivation of the antibiotic by β - Lactamases (pencillinases and ESBLs) • No cell wall (mycoplasma)
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Pencillin • The cornerstone of treatment for a large number of bacteria: – gram negative and gram positive cocci (neissera) – gram negative bacilli – spirochetes (syphilis) – anaerobes (not Bacteroides fragilis ) • very safe!
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This note was uploaded on 05/09/2010 for the course LMP 232 taught by Professor Crandall during the Spring '10 term at University of Toronto.

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18. Beta Lactams - -Lactam Antibiotics There is no such...

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