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14 Cards in this Set
- Front
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Name four drugs affecting bacterial cell wall |
Penicillins Cephalosporins Bacitracin Vancomycin |
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Describe penicillins and cephalosporins: structure, MoA & characteristics |
Structure: made up of beta lactam ring need for biological activity. Is target of bacterial resistance so the bacteria will make beta lactamases enzymes This has a side chain of beta lactamase ring which is target for degration of amydases by gastric juices These antibiotics going to work preventing peptiglycon of cell wall by cross linking
MoA: (1) bacterial cell wall made up of strands of peptiglycan (2) penicillin binding protein which is going to bind side chains of peptides by cross linking (3) protein is going to disassociate so then get formation of cross link (4) penicillin is going to go to active area of wherever the protein was so that interacts and inhibits the enzymes involved w cross linking (4) beta lactamase ring of penicillin going to remain irreversibly open during reaction of protein So penicillin will remain covalently linked to PBP so that blocks active site
Characteristics: Penicillins first line of treatment as effective against broad spectrum of gram positive/gram negative bacteria But both Cephlasporins/Penicillins not topical drugs as doesn't go through ocular barriers
Natural penicillins: penicillin G and penicillin V and 1st gen Cephlasporins cause hypersensitivities: type 1-4 - utacaria (hives), contact dermatitis, Steven Johnson syndrome & angioedema Also get nausea and diahorreha bc affects gut bacteria
Nb: Cephlasporins effective against gram negative bacteria but cause vit K deficiencies as prevents synthesis of bacteria responsible for making vit K thus won't have mature clotting factors so will get bleeding C/I in haemophillics
Synthetic penicillins: flucoxicillin (beta lactamase resistant), amoxicillin, ampicillin & penicillin all effective against P.auerginosa |
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Describe bacitracin: MoA & characteristics |
Bacitracin works bc prevents movement of precursor to peptidoglycan from cytoplasm, cell membrane to cell wall so inhibits cell wall synthesis
Characteristics: Low resistance to antibiotic and effective against gram positive but NOT gram neg excluding N.Gonhorreae Topical use only bc causes renal necrosis if used systemically Can be used topically on skin |
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Describe Vancomycin: MoA & characteristics |
MoA: Works bc prevents synthesis of peptiglycan as binds to mucopeptide precursor so prevents synthesis of cell wall
Characteristics: Low resistance and effective against gram positive bacteria esp those resistant to antibiotics ie used as last line of treatment - use for MRSA & C.difficle |
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Name 2 drugs affecting cell membrane permeability |
Gramicidin Polymixin b |
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Describe Gramicidin and Polymixin B |
Both work bc act like detergent - affects phospholipid component of cell wall so make cell leaky and attacks foreign substances
Gramicidin Effective against gram negative bacteria including P.aeurginosa Topical use only bc if used systemically causes neuro/nephrotoxic effects But can be used prophylactically when cornea / conjunctiva compromised Only comes in combo w steroid: Maxitrol
Polymixin B Effective against gram positive and gram negative excluding gram positive: bacilli Topical use only as causes haemolysis so affects blood CI in anyone w porphyria Can be used prohylactically when cornea / conjunctiva compromised Only comes in combo w steroid: Sofradex |
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Name five drugs affecting protein synthesis |
Aminoglycosides Tetracyclines Chloramphenicol Macrolidies Fusidic acid |
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Describe Aminoglycosides |
Binds irreversibly to 30s subunit of ribosome so moves along length of messenger rna so et amino acid chain so that protein can be made When Aminoglycoside binds to 50s subunit will change shape of mRNA so this can't be transcribed by tRNA Thus prevents adequate building of protein
Effective against gram positive and gram negative bacteria - excluding P auerginosa Mainly used for gonococcal keraconjunctivitis (characteristic white discharge) as its resistant to penicillin thus use Gentamicin
Drugs: Gentamicin Neomycin Tobramycin
Side effects Nephrotoxic and otoxotic effects Avoid if anyone using potentially ototoxic drugs - Cisplatin Not safe for use in pregnancy |
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Describe tetracyclines |
Prevents tRNA binding on 30s subunit of ribosome
Effective against gram positive / gram negative bacteria including P auerginosa / Proteus |
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Describe chloramphenicol |
Prevents elogation of protein by binding to 50s subunit of ribosome
Bacterial resistance: Bc bacteria made out of plasmids this can have mutations which is encoded for enzyme chloramphenicol transferases or can happen through chromosomal mutations which will affect outer membrane
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Describe macrolides |
Prevents elongation factor of protein by binding reversibly to 50s subunit
Bacterial resistance: through methylation of 23s subunit, active efflux and enzyme cleavage
Effective against gram P and some gram N bacteria but depends on which macrolide is used |
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Describe fusidic acid |
Prevents translocation of EF-G
Bacterial resistance can happen through alterations of EF-G
Drug: Fucathlmic 1% viscous drops (BAK/EDTA) |
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Name drugs involved in nucleic acid synthesis |
Quinolones/Fluoroquinolones |
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Describe Quinolones/Fluoroquinolones |
Works by binding alpha subunit of DNA gyrases so prevents supercoiling of DNA
Bacterial resistance through altered alpha subunits and altered porins so get decreased uptake of it
Effective against gram P and some gram N bacteria
Local/systemic SE not likely as: well tolerated, rare hypersensitivities & comfortable
Drugs: Ofloxacin Ciprofloxacin Levofloxacin Moxifloxacin
Nb Ciprofloxacin causes white corneal deposits but they are reversible once stop using drug |
