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Flashcards in protein synthesis inhibition abx Deck (18):

Which antibiotics target which parts of bacterial protein synthesis? Static/cidal designation

30S inhibitors: A and T: aminoglycosides (bactericidal) and tetracycline (static)
50S inhibitors: CELL: chlroamphenicol, clindamycin; erythromycin (macrolides), linezolid. all static except linezolid, which is variable


Aminoglycosides: examples, mechanism

gentamicin, neomycin, amikacin, tobramycin, streptomycin.
inhibit the 30S subunit and prevent formation of the initiation complex. cause misreading of mRNA. block translocation. require O2 for uptake, so they are ineffective for anaerobes.
(remember that A initiatiates the alphabet)


Aminoglycosides: resistance

all anaerobes are resistant because aminoglycosides require O2 for uptake.
bacteria gain resistance by inactivating the drug: acetylation, phosphorylation, or adenylation


Aminoglycosides: use

used for severe gram negative rod infection. synergy with beta lactams. give neomycin for bowel surgery


Aminoglycosides: toxicity

nephrotoxicity, esp. when used with cephalosporins, neuromuscular blockade, ototoxicity (esp. when used with loop diuretics), teratogenic


tetracycline: mechanism and resistance

bacteriostatic and bind the 30 S subuint. prevent attachment of aminoacyl-tRNA to ribosome (prevents elongation). limited CNS penetration. resistance: decr. uptake or incr. efflux by plasmid-encoded pumps.


tetracycline: special considerations

don't take with milk or antacids or iron-containg preps because divalent cations like Ca, Fe, Mg inhibit tetracycline absorption in the gut


tetracycline use

borrelia burdoferi, mycoplasma pneumonia. Accumuates intracellularly, so it works well against rickettsia and chlamydia. used for acne


tetracycline toxicity

GI distress, discoloration of teeth and inhibition of long bone growth in kids, photosensitivity. contraindicated in pregnancy


Macrolide mechanism and resistance

binds 50S and blocks translocation (mac-no-slides). (binds 23S rRNA). resistance: methylation of 23S rRNA-binding site.


Macrolide uses

atypical pneumonias (mycoplasma, legionella, chlamydia), STDs for chlamydia, and gram-positive cocci (step infections in ppl w/ penicillin allergies)


Macrolide toxicity

clarithromycin is embryotoxic and should be avoided in pregnancy.
MACRO: GI motility issues, arrhythmia and long QT, acute cholestatic hepatitis, rash, eosiniophilia. incr. serum conc. of theophyllines, oral anticoagulants


chloromphenicol mechanism

blocks peptidyl transferase at 50S ribosomal subunit. inactivated by plasmid-encoded acetyltransferace


Chloromphenicol use

menigitis (esp. Hib, N. menigitidis, S. pneumo), and Rocky Mountain Spotted fever.
limited d/t toxicities


chloramphenicol toxicities

anemia, aplastic anemia gray baby syndrome in premature infants b/c they lack liver UDP-glucuronyl transferase


Clindamycin mechanism

blocks peptide transfer (translocation) at the 50 S subunit (much like chloromphenicol).


Clindamycin uses

anaerobic infections in aspiration pneumonia, lung abscesses, and oral infections. also effective against invasive GAS infection. (anaerobes above the diaphragm)


Clindamycin toxicity

pseudomembranous colitis, fever, diarrhea, C diff.