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50 Cards in this Set
- Front
- Back
what is the MOA of chloramphenicol? Is it cidal or static?
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1) inhibits transpeptidation by blocking the binding of the rRNA to the mRNA... inhibits 50S peptidyltransferase activity
2) static |
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What is the MOA of macrolides, telithromycin and clindamycin?
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bind to 50S ribosome and block transpeptidation
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What is the MOA of tetracyclines?
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bind 30S ribosome and prevent tRNA binding to mRNA
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What is the MOA of streptogramins?
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bind 50S subunit and constrict exit channel for polypeptide and also inhibit tRNA synthase acitvity
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Are streptogramins bactericidal or static?
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cidal
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Is linezolid cidal or static?
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static
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What is the MOA of linezolid?
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binds 23S portion of 50S subunit and blocks initiation by preventing formation of tRNA-ribosome-mRNA complex
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Can chloramphenicol inhibit mammalian ribosomes?
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yes mitochondrial ones
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Why do tetracyclines not effect mammalian protein synthesis?
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cells have efflux pumps
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Is chloramphenicol static or cidal?
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usually static
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Is chloramphenicol active against chlamydia? what is it used for?
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1) no
2) meningitis from: a. S pneumoniae b. N meningitidis c. H influenzae |
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How does resistance to chloramphenicol occur?
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plasmid gene that codes ofr acetyltransferases
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Clinically what is chloramphenicol a back up drug for?
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backup drug for: salmonella, pneumococcal and meningococcal meningitis in beta-lactam sensitive persons
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What is chloramphenicol occasionally used for?
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rickettsial infections, bacteroides fragilis
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What is chloramphenicol commonly used for?
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1) topical antimicrobial
2) Meningitis with: a. S pneumoniae b. N meningitidis c. Hib |
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What are the toxicities of chloramphenicol? In neonates?
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Bone marrow: decreased RBC maturation, aplastic anemia (may be fatal because it is irreversible)
Gray baby syndrome: low RBCs, cyanosis, cardiovascular collapse (note neonates do not have glucuronyltransferase and are most sensitive) |
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What drugs does chloramphenicol increase the half lives of?
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phenytoin, tolbutamide and warfarin
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Are tetracyclines bacteriostatic or cidal? broad or narrow spectrum?
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static and broad spectrum
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What is the mechanism of resistance to tetracyclines? Which drug is not effected by these modes of resistance?
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efflux pumps and ribosomal changes
tigecycline |
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What two species have multidrug efflux pumps that can resist tigecycline?
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proteus and pseudomonas
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Clinically what are tetracyclines the primary treatment of treat?
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mycoplasma pneumonaie in adults, chlamydia, rickettsia and vibrio, acne, Tularemia
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What are secondary uses of tetracyclines?
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syphillis, leptospirosis and in treatment of acne
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What are selective uses of tetracyclines? Name the specific drug with the specific organism!
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H pylori (tetracycline), lyme disease (doxycycline), meningococcal carrier state (minocycline)
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What is demeclocycline used for?
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inhibits renal actions to ADH used in in SIADH
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What is tigecycline used for?
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MRSA, VRE, beta-lactamase gram -, anaerobes, chlamydiae, and mycobacteria
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What are the side effects of tetracyclines?
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GI: life threatening colitis
Bone: fetal exposure causes tooth enamel dysplasia and irregular bone growth Liver: hepatic necrosis Renal: tubular acidosis, Faconis syndrome UV sensitivity (tetracyclines, esp demeclocycline) and reversible dizziness and vertigo (doxycycline and minocycline) |
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What is unique about how azithromycin accumulates?
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has higher levels in the tissues and phagocytes than others
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What is the means of resistance to macrolides in gram + organisms?
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efflux pump and a methlyase which alters ribosomal binding site of macrolides
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How are enterobacteriaceae resistant to macrolides?
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metabolizing esterases
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What is erythromycin used for clinically?
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URIs, STDS
Gram+ cocci, M pneumoniae, Cornybacterium, Campylobacter jejuni, C trachomatis, C pneumoniae, L pneumophila, B pertussis and Ureaplasma urealyticum |
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Is erythromycin active against beta-lactamase gram + cocci?
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yes except PRSP and MRSA
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Azithromycin has activity similar to erythromycin except that is also active against?
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H influenzae, M catarrhalis, and Neisseria, and C trachomatis because of its long half life
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Clarithromycin has similar spectrum as erythromycin but is used in what two infections?
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M avium and H pylori
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What are the adverse effects of macrolides in general?
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GI irritation via stimulation of motlin receptors, skin rashes and eosinophilia, prolonged QT, cholestatic hepatitis, eosinophilia, increases concentration of coagulant drugs
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Which drug causes a hypersensitivity of acute cholestatic hepatitis?
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erythromycin estolate
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Clarithromycin and erythromycin can increase the half-lives of what drugs?
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anticoagulants, carbamazepine, cisapride, digoxin, theophylline
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What is an example of a ketolide? What is its MOA and spectrum of action?
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1) telithromycin
2) similar to erythromycin 3) similar to erythromycin |
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What are the toxicities of telithromycin?
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severe hepatotoxicity, visual disturbances and fainting episodes
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How does resistance to clindamycin occur?
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methylation of 50S ribosome and enzymatic inactivation
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What organsims are intrinsically resistant to clindamycin?
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gram - bacteria because they don't allow penetration through outer membrane
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What is the main use of clindamycin?
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severe infections with bacteriodes
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When is clindamycin used as a backup drug?
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gram + cocci and p jeroveci with pyrimethamine
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Clindamycin is used for prophylaxis in what condition?
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valvular endocarditis when people are allergic to penicillins
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What are the toxicities of clindamycin?
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rashes, neutropenia, hepatic dysfunction
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What are the streptogramins?
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quinupristin-dalfopristin
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what can streptogramins be used to treat?
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MRSA, PRSP, VRSA and resistant E faecium, E faecalis
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What are the side effects of streptogramins?
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arthralgia-myalgia syndrome
can also potentiate cyclosporine, diazepam, NNRTIs and warfarin |
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What is linezolid used for?
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MRSA, PRSP, VRE, L monocytogenes and corynebacterium
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Is there cross resistance of linezolid with other 50S inhibitors?
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no because it binds the 23S rRNA of the 50S which is unique to it
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What are the side effects of linezolid?
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thrombocytopenia and neutropenia
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