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Z - Micro 06
Micro 06
| Question | Answer |
|---|---|
| Transpeptidase catalyzes the linkage between what and what? | repeating disaccharide units and amino-acids in the peptidoglycan layer of G+ and G- orgs |
| G- defense against penicillin | Altering the porins so penicillins can't get into the cell |
| Beta-lactamase | Enzyme that bacteria have to cleave the C-N bond in the beat-lactam ring |
| 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. |
| What is the biggest problem with giving patients penicillins? | anaphylactic reactions (delayed rash) |
| How are aminopenicillins better than Penicillin G? | Better G- coverage |
| How are penicillinase-resistant penicillins better than Penicillin G? | not susceptible to B-lactamase produced by bacteria like Staph |
| How are anti-pseudomonal penicillins better than Penicillin G? | Wider G- and G+ coverage, including P. aeruginosa; active against anaerobes |
| How are cephalosporins better than Penicillin G? | G+ and G- PLUS resistant to B-lactamase-producing bacteria |
| When to give Penicillin G? | Strep pneumoniae |
| Name 2 aminopenicillins | Ampicillin and Amoxicillin, better G- coverage (better penetration and better binding to transpeptidase), still inhibited by B-lactamase |
| Name 3 IV penicillins that are not susceptible to B-lactamase | 1. Methicillin, 2. nafcillin, and 3. Oxacillin I MET a NAsty OX. |
| What is the major organism that produces B-lactamase? | Staph aureus |
| 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) |
| Name the anti-pseudomonal penicillins | 1. Carboxypenicillin (Carbenicillin/Ticarcillin) and 2. Ureidopenicillins (Piperacillin/Mezlocillin) |
| Are anti-pseudomonal penicillins sensitive to penicillinase? | Yes. Staph are resistant to these drugs. |
| Name the B-lactamase inhibitors | 1. Clavulanic Acid, 2. Sulbactam, 3. Tazobactam |
| 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 |
| What drugs are resistant to cephalosporins? | MRSA (changed the structure of its transpeptidase) and Enterococci (like Strep faecalis), Listeria, and Atypical pneumonias like mycoplasma |
| When to use First generation cephalosporins? | Need G+ coverage, before surgeries to prevent infection from the skin, when pts are allergic to penicillins; "ceph" |
| 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" |
| When to use Third generation cephalosporins? | Multi drug resistant aerobic G-, hospital-acquired strains; "ceft" |
| When to use Fourth generation cephalosporins? | Cefepime for Multi drug resistant aerobic G-, hospital-acquired strains PLUS p.aeruginosa |
| Which cephalosporin has the best CSF penetration? | Ceftriaxone (3rd generation) |
| What is first drug to treat meningitis? | Ceftriaxone (3rd generation cephalosporin) |
| 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) |
| 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. |
| 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. |
| Aztreonam | Covers G- (binds transpeptidase of G- only!), AEROBIC has only 1 beta lactam ring |
| Bacterial ribosome | 50S + 30S = 70S |
| CLEan TAG | 50S: C = Chloramphenicol, Clindamycin; L = Linezolid; Erythromycin. 30S: T = Tetracycline/Doxycycline (-thromycins); AG = Aminoglycoside (-micin/-mycins) |
| Which of the anti-ribosomal abx can NOT be taken orally? | AG's |
| What does Chloramphenicol cover? | most clinically important bacteria: G+, G-, anaerobic. Used for meningitis of the SHiN: Strep pneumoniae, Haemophilus influenza, Neisseria meningitidis. |
| 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 -- |
| Gray baby syndrome | toxocity of chloramphenicol (G+, G-, anaerobics inc B fragilis) |
| What does Clindamycin cover? | ANAEROBES, G+, gyn infxns; anaerobes above the diaphragm. (Bacterioides, C. perfringens) |
| Mechanism of clindamycin | blocks peptide bond formation at 50S ribosomal subunit |
| 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 |
| How to diagnose C. diff --> pseudomembranous colitis? | C. diff organism or toxin the stool |
| How to treat pseudomembranous colitis due to C. diff? | Van and Metro cruise down: Vancomycin (cover G+ since Clostridium is G+), Metronidazole |
| Linezolid | G+, last resort for VRE (Vancomycin resistant enterococcus) |
| Erythromycin | G+, atypical pneumonias (Mycoplasma, Legionella, Chlamydia) |
| What is the DOC for pneumonia that is not hospitalized? | Erythromycin (anti-ribosomal, 50S) |
| What is the DOC for Legionnaire's dz? | Erythromycin (anti-ribosomal, 50S) |
| Name common macrolides | Attack 50S ribosomal units in bacteria, hit G+: erythromycin, azithromycin, clarithromycin (ACE) |
| Mechanism of macrolides | ACE - Azithromycin, Clarithromycin, Erythromycin. Inhibit protein synthesis by blocking translocation; bind to 23S rRNA of the 50S ribosomal subunit. Bacteriostatic. |
| What are macrolides used for? | ACE - Azithromycin, Clarithromycin, Erythromycin. UPS is positively My CLaN. URI's, pneumonia, STDs, G+, Mycoplasma, Chlamydia, Neisseria. |
| Side effects of erythromycin | VERY SAFE! GI irritation, very rare blocking of bile duct flow (cholestatic hepatitis) |
| Tetracycline | Anti-ribosomal, 30S, hits Chlamydia, Mycoplasma, Brucella, Rickettsia. Also Doxycycline. |
| Mechanism of tetracycline | bacteriostatic. Bind to 30S and prevents attachment of aminoacyl-tRNA. Limited CNS penetration. |
| Name the tetracyclines | Tetracycline, Doxycycline, dmemclocycline, minocycline |
| Can Doxycycline be used in patients with renal failure? | yes because it is fecally eliminated. Dobby gets rid of Doxy by pooping. |
| Should NOT take tetracyclines with what? | Milk, antacids, or Fe-containing foods because the divalent cations inhibit tetracycline absorptions in the gut. |
| 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. |
| Adverse effects of tetracyclines | Midget child (inhibit bone growth) with black teeth (discoloration of teeth), wearing sunglasses (photosensitivity) |
| Demeclocycline | a tetracycline, also an ADH antagonist; acts as a Diuretic in SIADH. |
| Peds patient comes in with rash that's very sensitive to sunlight, brown teeth, and hx of being on abx | Tetracycline/doxycycline. |
Created by:
christinapham
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