Micro 06
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| Transpeptidase catalyzes the linkage between what and what? | repeating disaccharide units and amino-acids in the peptidoglycan layer of G+ and G- orgs
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| G- defense against penicillin | Altering the porins so penicillins can't get into the cell
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| Beta-lactamase | Enzyme that bacteria have to cleave the C-N bond in the beat-lactam ring
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| How is MRSA resistant to all of the penicillins? | usually, penicillin binds to the transpeptidase. MRSA altered the structure of the transpeptidase so the beta-lactam ring of penicillins can't inhibit the enzyme.
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| What is the biggest problem with giving patients penicillins? | anaphylactic reactions (delayed rash)
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| How are aminopenicillins better than Penicillin G? | Better G- coverage
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| How are penicillinase-resistant penicillins better than Penicillin G? | not susceptible to B-lactamase produced by bacteria like Staph
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| How are anti-pseudomonal penicillins better than Penicillin G? | Wider G- and G+ coverage, including P. aeruginosa; active against anaerobes
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| How are cephalosporins better than Penicillin G? | G+ and G- PLUS resistant to B-lactamase-producing bacteria
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| When to give Penicillin G? | Strep pneumoniae
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| Name 2 aminopenicillins | Ampicillin and Amoxicillin, better G- coverage (better penetration and better binding to transpeptidase), still inhibited by B-lactamase
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| Name 3 IV penicillins that are not susceptible to B-lactamase | 1. Methicillin, 2. nafcillin, and 3. Oxacillin I MET a NAsty OX.
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| What is the major organism that produces B-lactamase? | Staph aureus
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| Name 2 oral penicillins that are not susceptible to B-lactamase | 1. CLOXacillin and 2. diCLOXacillin -- used for B-lactamase-producing G+ organisms (like staph aureus)
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| Name the anti-pseudomonal penicillins | 1. Carboxypenicillin (Carbenicillin/Ticarcillin) and 2. Ureidopenicillins (Piperacillin/Mezlocillin)
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| Are anti-pseudomonal penicillins sensitive to penicillinase? | Yes. Staph are resistant to these drugs.
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| Name the B-lactamase inhibitors | 1. Clavulanic Acid, 2. Sulbactam, 3. Tazobactam
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| What are the advantages of cephalosporins over penicillins? | B-lactam ring is more resistant to B-lactamase (but still susceptible to cephalosporinases) AND new R-group side chain lets us have many different formulations
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| What drugs are resistant to cephalosporins? | MRSA (changed the structure of its transpeptidase) and Enterococci (like Strep faecalis), Listeria, and Atypical pneumonias like mycoplasma
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| When to use First generation cephalosporins? | Need G+ coverage, before surgeries to prevent infection from the skin, when pts are allergic to penicillins; "ceph"
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| When to use Second generation cephalosporins? | Need coverage for pneumonia and don't know what the organism is (Strep pneumo and H flu is covered in these groups); "cef"
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| When to use Third generation cephalosporins? | Multi drug resistant aerobic G-, hospital-acquired strains; "ceft"
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| When to use Fourth generation cephalosporins? | Cefepime for Multi drug resistant aerobic G-, hospital-acquired strains PLUS p.aeruginosa
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| Which cephalosporin has the best CSF penetration? | Ceftriaxone (3rd generation)
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| What is first drug to treat meningitis? | Ceftriaxone (3rd generation cephalosporin)
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| Which abx has the broadest antibacterial activity of any known to man? | Imipenem (I'm a pen crossing out all the bacteria that are difficult to treat -- except MRSA and Pseudomonas and Mycoplasma)
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| What are the strengths and weaknesses of Imipenem? | NOT susceptible to B-lactamase produced by bacteria like Staph. IS susceptible to dihydropeptidase in the kidney, so must be given with cilastin, which inhibits that enzyme so that Imipenem won't be broken down.
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| Meropenem | Newer abx that has a beta-lactam ring. As powerful as Imipenem. Don't have to use in conjunction with Cilastin because it's not broken down by dihydropeptidase in the kidney.
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| Aztreonam | Covers G- (binds transpeptidase of G- only!), AEROBIC has only 1 beta lactam ring
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| Bacterial ribosome | 50S + 30S = 70S
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| CLEan TAG | 50S: C = Chloramphenicol, Clindamycin; L = Linezolid; Erythromycin. 30S: T = Tetracycline/Doxycycline (-thromycins); AG = Aminoglycoside (-micin/-mycins)
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| Which of the anti-ribosomal abx can NOT be taken orally? | AG's
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| What does Chloramphenicol cover? | most clinically important bacteria: G+, G-, anaerobic. Used for meningitis of the SHiN: Strep pneumoniae, Haemophilus influenza, Neisseria meningitidis.
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| Why is Chloramphenicol used only as a last resort? | Severe side effects: "chlorine" poured into bones --> reversible and dose-dependent anemia, irreversible aplastic anemia (drug wipes out all bone marrow permanently), gray baby syndrome (neonates can't fully conjugate the drug or excrete through kidney --
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| Gray baby syndrome | toxocity of chloramphenicol (G+, G-, anaerobics inc B fragilis)
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| What does Clindamycin cover? | ANAEROBES, G+, gyn infxns; anaerobes above the diaphragm. (Bacterioides, C. perfringens)
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| Mechanism of clindamycin | blocks peptide bond formation at 50S ribosomal subunit
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| What is the big side effect of Clindamycin? | Kills G+ and anaerobes, so wipes out the normal GI flora -- if Clostridium difficile is not killed, taking Clindamycin will lead to C. dif --> pseudomembranous colitis
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| How to diagnose C. diff --> pseudomembranous colitis? | C. diff organism or toxin the stool
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| How to treat pseudomembranous colitis due to C. diff? | Van and Metro cruise down: Vancomycin (cover G+ since Clostridium is G+), Metronidazole
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| Linezolid | G+, last resort for VRE (Vancomycin resistant enterococcus)
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| Erythromycin | G+, atypical pneumonias (Mycoplasma, Legionella, Chlamydia)
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| What is the DOC for pneumonia that is not hospitalized? | Erythromycin (anti-ribosomal, 50S)
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| What is the DOC for Legionnaire's dz? | Erythromycin (anti-ribosomal, 50S)
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| Name common macrolides | Attack 50S ribosomal units in bacteria, hit G+: erythromycin, azithromycin, clarithromycin (ACE)
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| Mechanism of macrolides | ACE - Azithromycin, Clarithromycin, Erythromycin. Inhibit protein synthesis by blocking translocation; bind to 23S rRNA of the 50S ribosomal subunit. Bacteriostatic.
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| What are macrolides used for? | ACE - Azithromycin, Clarithromycin, Erythromycin. UPS is positively My CLaN. URI's, pneumonia, STDs, G+, Mycoplasma, Chlamydia, Neisseria.
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| Side effects of erythromycin | VERY SAFE! GI irritation, very rare blocking of bile duct flow (cholestatic hepatitis)
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| Tetracycline | Anti-ribosomal, 30S, hits Chlamydia, Mycoplasma, Brucella, Rickettsia. Also Doxycycline.
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| Mechanism of tetracycline | bacteriostatic. Bind to 30S and prevents attachment of aminoacyl-tRNA. Limited CNS penetration.
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| Name the tetracyclines | Tetracycline, Doxycycline, dmemclocycline, minocycline
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| Can Doxycycline be used in patients with renal failure? | yes because it is fecally eliminated. Dobby gets rid of Doxy by pooping.
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| Should NOT take tetracyclines with what? | Milk, antacids, or Fe-containing foods because the divalent cations inhibit tetracycline absorptions in the gut.
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| What to use tetracyclines for? | Tetracyclines VACUUM THe BedRoom. Vibrio cholera, acne, Chlamydia, Ureaplasma urealyticum, Mycoplasma pneumoniae, Tularemia, H pylori, Borrelia burgdorferi (Lyme dz), Rickettsia.
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| Adverse effects of tetracyclines | Midget child (inhibit bone growth) with black teeth (discoloration of teeth), wearing sunglasses (photosensitivity)
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| Demeclocycline | a tetracycline, also an ADH antagonist; acts as a Diuretic in SIADH.
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| Peds patient comes in with rash that's very sensitive to sunlight, brown teeth, and hx of being on abx | Tetracycline/doxycycline.
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