antibiotic actionW13s

Antibiotic actionW13s

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Unformatted text preview: esistance: •  due to possession of β-lactamase (penicillinase) activity •  &/or altered penicillin binding proteins (PBPs) by the resistant bacteria antib11 peptidoglycan assembly: -autolysins break down peptidoglycan -wall always has to be replacing it self -cell has to be actively making peptidoglycan -pen. only afects active cells -bactericidal b/c cell bursts transpeptidases: •  also known as penicillin binding proteins (PBPs) •  activity disrupted by penicillin binding (Fig 6.7 Madigan et al. 12th ed; Fig. 6.5 11th ed) -use if people are allergic to pen. antib12 cephalosporins: •  structurally different molecules than penicillins; also possess β-lactam ring •  clinically important ones are semi-synthetic, have broader spectrum of activity than penicillins, more resistant to β-lactamases e.g., ceftriaxone: drug of choice for treating gonorrhea (many N. gonorrhea strains now penicillin-resistant) lactam ring 6-member thiazolidine ring (Prescott et al. 2005) antib13 s: •  produced by strains of Streptomyces •  broad-spectrum - inhibit most grampositive & gram-negative bacteria •  affect protein synthesis •  interfere with 30S RSU function → prevents aa-tRNA binding •  bacteriostatic (bind reversibly) •  natural & semisynthetic s used clinically s (Fig 27.23 Madigan et al. 12th ed; Fig. 20.23 11th ed) •  been widely used in human medicine •  also been used in veterinary medicine •  been used as nutritional supplement for poultry, pigs → widespread antibiotic resistance antib14 macrolides: •  reversibly bind 23S rRNA of 50S RSU •  effective against variety of bacteria, including many gram positives, mycoplasmas, Chlamydia, Legionella •  ineffective against Enterobacteriaceae (cannot cross OM) •  often drug of choice for patients with penicillin allergy •  e.g., erythromycin (Streptomyces erythreus), azithromycin, clindamycin •  e.g., treatment of walking pneumonias, whooping cough, campylobacteriosis erythromycin (Fig 27.22 Madigan et al. 12th ed) polymyxin B: bacillis •  binds to membrane of gram negative bacteria → altered permeability, cellular leakage → death •  has much the same effect on eukaryotic membranes → topical applications only (first aid skin ointments) antifungal and antiviral drugs: antib15 •  far fewer are available •  host toxicity is an issue •  fungi are eukaryotes •  viruses make use of host cellular functions antifungal agents: •  some useful as topical agents only •  e.g., several azoles •  ergosterol = major target •  in most fungi; in place of cholesterol (present in other eukaryotic cell membranes) •  polyenes - bind ergosterol •  azoles - inhibit ergosterol synthesis •  echinocandins – inhibit fungal 1,3-β-D glucan synthase (involved in fungal cell wall synthesis) •  mammalian cells lack enzyme, walls •  e.g., treatment of Candida infections antifungal chemotherapeutic agents (Fig 27.26 Madigan et al. 12th ed; Fig. 20.24 11th ed) antib16 antiviral agents: •  difficult targets for selective toxicity → aim at virus-only targets; only know of a few •  disrupt uncoating → prevents viral replication •  amantadine (influenza A) •  nucleoside analogs → phosphorylation & incorporation terminates growing nucleotide chain •  (Herpes), AZT (HIV) -base mis-pairing •  target viral polymerase •  target reverse transcriptase •  target virally-encoded enzymes •  protease inhibitors (HIV), NA inhibitors (influenza) (Nester et al., 2004)...
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This note was uploaded on 03/16/2013 for the course BIOL 449 taught by Professor Barbrabulter during the Winter '13 term at Waterloo.

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