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Z - Micro 06

Micro 06

QuestionAnswer
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