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jskunz
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Who was Paul Ehrlich
- German physician and bacteriologist
- began searching for "magic bullet", a drug that would kill a microbial pathogen w/o harming the human host
- Was looking for sure for syphilis
- The 606 drug compound he tested proved highly effective in txing dx in lab animals
- Drug called Salvarsan
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Who was Gerhard Domagk
discovered red dye called Protosil which could be used to treat streptococcal infections in animals
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chemotherapeutic agents
chemicals used to treat disease
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Who were Ernst Chain and Howard Florey
successfully purified penicillin compound
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antibiotics
antimicrobial drugs naturally produced by microorganisms
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selective toxicity
exhibited by antimicrobial drugs, as they cause greater harm to microbes than to human host
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therapeutic index
the lowest dose toxic to patient divided by dose typically used for therapy
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Bacteriostatic
inhibits bacterial growth
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bactericidal
kills bacteria
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intrinsic (innate) resistance
- resistance due to inherent characteristics of organism
- Ex: If a species lacks a cells wall, will be resistant to penicillin as that's what penicillin attacks
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acquired resistance
when sensitive organisms develop resistance by spontaneous mutation or horizontal gene transfer
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β-lactam drugs
- bactericidal against variety of bacteria
- Includes penicillins, cephalosporins, monobactams and carbapenems
- Competitively inhibit enzymes that catalyze formation of peptide bridges in peptidoglycan synthesis (for cell wall)
- These enzymes bind penicillin, which causes disruption in cell wall synthesis = weakens wall, causing cell to lyse
- *Are bactericidal only against growing bacteria, as these cells continually synthesize peptidoglycan
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PBP's
- Penicillin-binding proteins
- enzymes that are affected by β-lactam drugs
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What is different btwn the different β-lactam drugs
- the vary in their spectrum of activity
- The peptidoglycan of gram+ is exposed on outside, drug can reach target. But Peptidoglycan of gram- is on inside preventing drug from reaching target
- Another difference is PBP's...
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β-lactamase
an enzyme that breaks the critical β-lactam ring, destroying the activity of the antibiotic
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Natural penicillins
The original penicillins produced naturally by the mold Penicillium chrysogenum
Narrow-spectrum - effective against gram+ & a few gram-
- *Bacteria that produce penicillinase are resistant to natural penicillins
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Penicillinase-resistant penicillins
- Lab developed in response to penicillinase-producing Staphylococcus aureus strains
- include methicillin and dicloxacillin
- *Unfortunately, some penicillinase-producing bacteria acquired ability to make altered PBP's to which β-lactam no longer bind
- S. aureus strains that can do this are called MRSA
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Broad spectrum penicillins
- have modified side chains, giving them broad spectrum of activity
- retain their activity against penicillin sensitive gram+, yet also active against gram -
- Unfortunately, can be inactivated by β-lactamases
*Includes ampicillin and amoxicillin
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Extended-spectrum penicillins
- Have greater activity against Pseudomonas species - gram- bacteria that are unaffected by many antimicrobial drugs
- Has less activity against gram+ bacteria
- Include Ticarcillin and Piperacillin
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Penicillins + β-lactamase inhibitor
- combo of agents
- inhibitor interferes with activity of some types of β-lactamases, thereby protecting the penicillin against enzymatic destruction
Includes Augmentin
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Vancomycin
- blocks peptidoglycan synthesis by binding to peptide side chain of NAM molecules being assembled to form glycan chains
- weakens cell, causing lysis
- Used to treat C diff infections
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Bacitracin
inhibits cell wall biosynthesis by interferring with transport of peptidogycan precursors across cytoplamsic membrane
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Aminoglycosides
- are bactericidal drugs that irreversibly bind to 30S ribosomal subunit, causing it to distort and malfunction
- blocks initiation of translation and causes misreading of mRNA by ribosomes that have already passed initiation step
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Tetracyclines
reversibly bind to 30S ribosomal subunit, blocking the attachment of tRNA and preventing translation from continuing
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Glycylcyclines
related to tetracyclines, same mechanism of action and effect, but wider spectrum of activity
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Macrolides
- reversibly bind to 50S ribosomal subunit and prevent the continuation of translation
- Often serve as drug of choice for pt's who are allergic to penicillin
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Chloramphenicol
binds 50S ribosomal subunit, preventing peptide bonds from being formed and blocking translation
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Lincosamides
bind to 50S ribosomal subunit and prevent continuation of translation
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Oxazolidinones
bind to 50S ribosomal subunit, interfering with the initiation of translation
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Streptogramins
- 2 streptogramins are administered together (quinupristin and dalfopristin) called Synercid
- act as synergistic combo, bonding 2 different sites on 50S ribosomal subunit and inhibiting distinct steps of translation
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