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MICABI - Exam 1
Lecture 3
| Question | Answer |
|---|---|
| Drug that are cell wall synthesis inhibitors (4) | Penicillins, Cephalosporins, Vancomycin, Daptomycin |
| Drugs that are inhibitors of protein synthesis (4) | Aminoglycosides, chloramphenicol, macrolides, tetracyline |
| Drugs that are antimetabolites (2) | Sulfonamides and Trimethoprim |
| Drugs that affect membrane permeability (2) | Polymyxin B, Gramicidin |
| Drugs that affect DNA replication & repair | Fluroquinolones |
| Gram-positive bacteria structure features | Cytoplasmic membrane, thick peptidoglycan, capsule, pilus, teichoic acid |
| Gram-negative bacteria structure features | Cytoplasmic membrane, periplasmic space, thin peptidoglycan, out membrane with porins, capsule, pilus |
| cell wall feature that gives rigidity, maintains the balance of osmotic pressure and keeps bacterium from lysing | peptidoglycan |
| Bacteria cell wall made of this kind of sugar linkage | alpha 1,4-glycosidic linkages |
| bacteria specific peptide linkage | D-Ala-D-Ala peptide linkage (links nearby sugars) |
| first stage of baterial cell wall synthesis | Formation of UDP-AMP inside the cell |
| function of UDP-AMP | cross-linker unit |
| second stage of bacterial cell wall synthesis | Transfer of UDP-AMP through the membrane with modification and linkage to the cell wall |
| Vancomycin works on this stage of cell wall synthesis | second stage (addition of the single unit - UPD-AMP - linkage to the cell wall) |
| third stage of bacterial cell wall synthesis | Once inserted into the wall cross-linking reactions and modification of the wall components |
| Penicillins and cephalosporins work on this stage of cell wall synthesis | third stage (peptide cross-link formation between carbohydrate polymers) |
| how does vancomycin bind to D-Ala-D-Ala | via hydrogen bonds |
| polypeptide antibacterial inhibitors are active against which organisms | they are only active against gram-positive (dont get taken up by gram-negative membrane very well) |
| polypeptide antibacterial inhibitors (3) | Vancomycin, Teicoplanin and Bacitracin |
| Van A resistance gene | confers resistance to vancomycin and teicoplanin is inducible and most likely on a transferable plasmid |
| Van B & C resistance genes | confers resistance to vancomycin only - Van B is chromosomal and non-transferable |
| in high level resistance, D-Ala-D-Ala peptidoglycan gets replaced with this | D-Ala-D-lactate |
| new drug (lipopeptide) that is bactericidal to resistant gram positive pathogens | Daptomycin |
| Daptomycin currently approved for this use | Complicated Skin and Skin Structure Iinfections (CSSSI) |
| Daptomycin mechanism | Binds irreversibly to the cytoplasmic membrane, depolarizes the membrane in a calcium dependent manner |
| Daptomycin is a potent bactericidal against these gram positive resistant organisms | VRE and MRSA |
| Penicillins and Cephalosporins (B-lactams) mimick this peptide | D-Ala-D-Ala |
| B-lactams are these types of enzymes | PBP 1a & 1b - transpeptidases |
| B-lactamases may have evolved from these | penicillin binding proteins (PBP) |
| bacterial strains deficient in this, are susceptible to inhibition of transpeptidase, but not lysis | autolysin |
| 3 factors determining activity of Cephalosporin or Penicillins | 1) Binding affinity for target enzymes 2) Ability to penetrate the outer membrane envelope 3) Sensitivity to inactivation by b-lactamase |
| two main components of beta-lactam antibiotic structure | Thiazolidine ring and Beta-lactam ring |
| Broad spectrum antibiotics are based on this ability | ability to penetrate the gram-negative cell membrane |
| Penicillins Group I and II spectrum | Narrow Spectrum |
| natural penicillins (narrow spectrum) | Penicillin G, Pen V |
| Penicillins Groups III and IV spectrum | Broad Spectrum |
| broad spectrum penicillins (2) | ampicillin and amoxicillin |
| only class of penicillins that have activity against pseudomonas | ureidopenicillins (group V) |
| two main components of cephalosporin antibiotic structure | Dihydrothiazine ring and beta-lactam ring |
| in which type of bacteria are beta-lactamases a problem | gram-negative bacteria |
| beta-lactamase resistance is due to this mechanism | hydrolyzing the lactam ring |
| where is beta-lactamase in gram-positive bacteria | excreted out into the environment (gets diluted, so less likely to hydrolyze the lactam ring) |
| where is beta-lactamase in the gram-negative bacteria | sitting in the periplasmic space (chances of the drug getting hydrolyzed are much higher) |
| high conservation between these bacterial enzymes suggests common ancestry | beta-lactamases and the D-Ala carboxypeptidases |
| MRSA determined by this | chromosomal gene transferred by transduction (requires penicillinase plasmid) |
| supplementary PBP's acquired in MRSA have this | lowered affinity for methicillin and other b-lactams |
| drug of choice for MRSA infections | Vancomycin (with rifampin in life threatening cases) |
| b-lactamase Inhibitors | Tazobactam and clavulanic acid |
| Tazobactam | latest beta-lactamase inhibitor developed has the same mechanism as clavulanic acid but is more potent |
Created by:
Krafty
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