Microbio - antimicrobials Flashcards
How do B-lactams work?
Blocks transpeptidase cross-linking of peptidoglycan in cell wall (weakened cell wall –> osmotic lysis)
Note: these are D-ala-D-ala analogs, thus blocking transpeptidase
Which drugs are B-lactams?
Penicillin, amox/ampicillin, cephalosporins, carbapenems, monobactams
How do bacitracin and vancomycin work?
Similar to B-lactams, but they block peptidoglycan synthesis (as opposed to blocking the cross-linking)
Mechanism: bind D-ala D-ala portion of cell wall precursors (pay back 2 D-alas for van-dalizing)
Protein synthesis inhibitors (buy AT 30, CCEL at 50)
30S inhibitors: Aminoglycosides = irreversible (genta, neomycin, amikacin, tobra, strepto) and Tetracyclines = static (tetra, doxy, mino
)50S inhibitors: Chloramphenicol, Clindamycin, Erythromycin (macrolides, azithro, clarithro), Linezolid
Aminoglycosides special things to know (side effects, uptake)
Side effects: nephro, ototoxicity, teratogen
Requires O2 for uptake, therefore can’t use for anaerobes (Nocardia, Pseudomonas, myco TB)
Tetracyclines things to know
Doxy is used in renal failure pts
Don’t give with divalent cations (Fe, Ca, Mg), they decrease absorption of the drug
Anaerobic infection tx
Above diaphragm: clindamycin (aspiration pneumo, lung abscesses, oral infxns)
Below diaphragm: metronidazole
Macrolides special factsside effects (MACRO)
Bind 23S subunit of 50S, block translocation
Motility issues Arrythymias Cholestatic hepatitis Rashe Osinophilia
Folate synthesis inhibitors (Bactrim)
Trimethoprim - inhibit DHF reductase, TMP - treats marrow poorly (lots of -penias)
Sulfonamide - metabolites inhibit dihydropteroate synthase, watch out in G6PDH, can displace warfarin
Fluoroquinolones (levofloxacin, cipro, xacin)
inhibit DNA gyrase and topoisomerase IV
- hurt attachments to your bones! tendon problems in elderly and steroid pts
Metronidazole
forms toxic free radicals in the bacterial cell wall
disulfiram-like with alcohol
metallic taste
Anti-mycobacterial (red body fluids, B6, optic neuropathy)
R: rifampin (4 R’s = RNA pol inhibitor, Ramps up p-450, Red/orange urine, Rapid resistance alone
)I: isoniazid = decreased mycolic acid (cell wall), requires bacterial activation, used as solo ppx, give with B6 (INH hurt Neuron and Hepatos)
P: pyrazinamide
E: decreased cell wall polymerization, optic neuropathy (color blindness)!
Antifungals
Amphotericin B/Nystatin - forms pores by binding ergosterol
Flucytosine - used with Ampho, inhibit DNA/RNA synth
Azoles - inhibit p450, which makes ergosterol
Terbanifine - inhibit squalene epoxidase
Chloroquine resistance mech
Blocks detox of heme in hemozoin (heme is toxic to malaria)
resistance arises due to membrane pump that decreases [drug]i
Antiviral therapy
release of progeny virus
nucleic acid synthesis
protein synthesis
release of progeny - oseltamivir (inhibit influenza neuraminidase)
nucleic acid synthesis - guanosine analogs, inhibit viral DNA polymerase by chain termination (acyclovir: HSV, VZV) (ganciclovir: CMV) (last line: foscarnet: binds to polymerase)
protein synthesis - IFN-a, -B (MS), -y (CGD)
