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70 Cards in this Set

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polymyxin B (and ciprofloxacin)
selective activity against G- enteric rods, esp against Pseudomonas
polymyxin B
positively charged polypeptide antibiotic binds first to negatively charged LPS in the outer membrane, then to cytoplasmic membrane phospholipids, causing membrane leakage
polymyxin B
commonly used as topical agents--systemic use largely supplanted by more effective and less toxic agents
polymyxin B
affects membrane permeability
streptomycin
no longer widely used in therapy except in TB
streptomycin
discovered in deliberate search for antibiotics produced by soil bacteria, extended range of antibiotic therapy to mycobacterium tuberculosis and many gram-negative organisms for which there had not been an effective treatment
streptomycin
positively charged at physiological pH
streptomycin
does not penetrate bacteria readily
streptomycin
some metabolic activity by bacterium needed for antibiotic to enter
streptomycin, gentamycin
requires aerobic conditions to be effective, inhibited under anaerobic conditions or acid conditions
streptomycin
bacteriocidal but not lytic
streptomycin
action on 30S ribosomal subunit, shown by mixing sensitive and resistant subunits in criss-cross experiment and reconstitution of 30S subunits from individual RNA and protein molecules
streptomycin
at low concentrations binds specifically to 30S ribosomal protein, distorting acceptor site, causing misreading, which causes bad proteins to be made, membrane leakiness, and increase in antibiotic uptake
streptomycin
molecules enter cell through imperfections in growing membrane
streptomycin
high concentrations: inhibits formation of initiation complex and peptide bond formation
streptomycin
resistant mutants readily obtained; mutation occurs before contact with antibiotic, which selects for mutants by providing environment that favors their growth while inhibiting non-resistant bacteria
gentamicin
interacts with more than one ribosomal protein on 30S subunit, can't obtain resistance in one step
gentamicin
toxic effects, damaging 8th cranial nerve or renal function
tetracycline, doxycycline
blocks binding of aminoacyl-RNA to 30S ribosomal subunit
tetracycline, doxycycline
well-absorbed orally and suited to out-patient treatment when therapy needed over a week or two
tetracycline, doxycycline
broad spectrum of action, including mycoplasma, rickettsia, chlamydia
tetracycline, doxycycline
not to be given in pregnancy because of possible adverse effects on fetus--some serious some minor
tetracycline, doxycycline
up to age of 8, children develop mottled enamel
tigecycline
most potent tetracycline dreivative
tigecycline
chemical side-chain that makes it refractory to common mechanism of resistance with efflux pump
erythromycin, azithromycin
blocks chain elongation
erythromycin
widely used therapeutic agent with spectrum of activity similar to penicillin G but includes mycoplasma and chlamydia
azithromycin
oral drug related to erythromycin but with higher activity and slightly broader spectrum
azithromycin
high and sustained tissue concentrations (T 1/2 = 70hr), which increase at site of infection--attributable to uptake by phagocytes which migrate to site
chloramphenicol
bacteriostatic, though in some bacterial species cessation of growth leads to cidal effect
chloramphenicol
rarely induces uncommon but sometimes lethal, aplastic anemia
chloramphenicol
useful against some anaerobes, particularly bowel anaerobes such as B. fragilis
chloramphenicol
in the U.S., dispensing requires prescription; other countries, sold over thecounter
clindamycin
derivative of lincomycin
clindamycin
activity against G+ and moderate activity against anaerobes
clindamycin
inhibits peptidyl transfer
oxazolidinones
first new class of anti-ribosomal drugs to be developed in 35 years
oxazolidinones
highly active against G+ organisms
oxazolidinones
potential for treating especially VREF, but also potentially MRSA, VRSA, and other multiply resistant bacteria
linezolid (Zyvox)
prototype of oxazolidinones
oxazolidinones
excellent pharmacokinetics, equal bioavailability by both oral and intravenous routes and no need for dose adjustment in patients with renal impairment
oxazolidinones
inhibit tRNA translocation
oxazolidinones
interacts with 16S RNA and 23S rRNA of the 30S and 50S ribosomal subunits
oxazolidinones
site of interaction determined by characterizing antibiotic resistant mutants
sreptogramins
clinical prototype is combination of dalfopristin and quinupristin (synergin)
dalfopristin
plus quinupristin = Synergin
quinupristin
plus dalfopristin = Synergin
Synergin
quinupristin + dalfopristin, 16-fold more active that either alone
sreptogramins, oxazolidinones
potential for treating MRSA, VREF, and other multiply resistant bacteria
mupirocin
binds specific tRNA synthetase (isoleucyl-tRNA synthetase) and prevents its function, resulting in no charged Ile-tRNA's available for protein synthesis
mupirocin
bacteriostatic at low concentrations but bacteriocidal at high concentrations achieved by topical administration, perhaps due to lack of incorporation of isoleucine into protein chains in cell wall
mupirocin
useful for treatment of MRSA, especially against nasal carrier state
mupirocin
for topical treatment of impetigo caused by S. aureus or S. pyogenes, weaker against natural surface flora
ciprofloxacin, moxifloxacin
active vs. G- enteric bacilli, some G+ cocci, and P. aeruginosa
ciprofloxacin, moxifloxacin
used for UTI, respiratory, and anaerobic infections
ciprofloxacin
therapeutic treatment of anthrax
ciprofloxacin
prophylactic when exposure to B. anthracis is potential risk, such as in first responder situation
ciprofloxacin, moxifloxacin
inhibits DNA gyrase necessary for DNA synthesis. bacteriocidal
ciprofloxacin, moxifloxacin
resistance emerging rapidly, no longer recommended for treating MRSA
ciprofloxacin, moxifloxacin
not for pregnant women or children b/c they can damage growing bone
metronidazole
binds DNA and fragments it
metronidazole
useful against anaerobic bacteria, especially Bacteriodes species
metronidazole
used for certain protozoal infections (trichomoniasis and amebiasis)
metronidazole
action requires anaerobic conditions--antibiotic is reduced and activated by electron transport protein (ferredoxin)
rifampin
broad spectrum, inhibits transcription by binding to B subunit of bacterial RNA polymerase, inhibiting specific binding to DNA
rifampin
often used in combination with other antibiotics since resistance develops rapidly when used alone, used with isoniazid or pyrazinamide as major therapies against tuberculosis
rifampin
efficiently secreted in saliva, so useful as prophylactic against infectious bacteria that enter via nasopharyngeal route
rifampin
prevents spread of N. menigitidis
ethambutol
antituberculosis drug; mechanism of action unknown, bacteriostatic against tubercle bacilli
pyrazinamide
antituberculosis drug; mechanism of action unknown, bacteriocidal drug that requires activity of Mycobacteria amidase to become activated