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11 Cards in this Set
- Front
- Back
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Cephalosporin Structure
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- Beta-lactam ring with 6-membered dihydrothiazine ring (instead of 5-membered as in penicillins.
- 6-membered dring provides stability against many Beta-lactamase enzymes that render penicillins inactive. |
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Structural Modifications of Cephalosporin Structure
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- Modifications at position 7 of beta-lactam ring --> changes in antibacterial activity.
- Changes at position 3 of dihydrothiazine ring --> changes in pharmacokinetic properties. |
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Cephamycins
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- Cephalosporins with a methoxy group at position 7 of the beta-lactam ring.
- Modification confers activity against anaerobes like Bacteroides |
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Cephalosporin Mechanism
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- Interfere with cell wall synthesis by binding to and inhibiting PBPs in the cell walls of bacteria
- Results in unstable cell that leads to decreased bacterial growth, cell lysis, and death - BACTERICIDAL |
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PBPs
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- Transpeptidases
- Carboxypeptidases - Endopeptidases --> Responsible for peptidoglycan cross-linking |
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Organisms that produce beta-lactamase enzymes
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GRAM NEG: H. influenzae, N. gonorrhoeae, M. catarrhalis, K. pnemoniae, E. Coli, Proteus spp., P. aeruginosa, S. marcescens, etc.
GRAM POS: S. aureus, etc. ANAEROBIC: B. fragilis |
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Cephalosporin susceptibility to Beta-lactamases
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Susceptibility varies among beta lactamases
3rd and 4th generation cephalosporins are most resistant to gram-negative produced beta-lactamase enzymes. |
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SPICE Bacteria
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Have ability to produce beta-lactamase enzymes when exposed to antibiotics that induce their production --> INDUCIBLE BETA-LACTAMASES
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1st GENERATION CEPHALOSPORIN ACTIVITY
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- BEST FOR GRAM POSITIVE AEROBES
- Limited activity against a number of gram-negative aerobes. |
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2nd and 3rd GENERATION CEPHALOSPORIN ACTIVITY
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Increasing activity against gram-negative aerobes (from 1st to 3rd generation) with decreasing gram-positive activity.
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4TH GENERATION CEPHALOSPORIN ACTIVITY
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- Active against BOTH GRAM-POSITIVE and GRAM-NEGATIVE AEROBES
- Greater stablity against beta-lactamase enzymes as you move through the generations |
