PCN/cephs: production of beta lactamases which leave the beta lactam ring structure, change in PCN binding proteins
Aminoglycosides: formation of enzymes that inactivate drugs via conjugation reactions that transfer acetyl, prosphoryl, or adenylyl groups
Marcolides: Formation of methyltransferases that alter drug binding sites on the 50s subunit
ANTIBIOTIC
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MECH OF ACTION
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AFFECTED ORGANISMS
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MECH OF RESISTANCE/COMMENTS
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Beta lactams- narrow spectrum
-PCN G
-PCN V
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-Bactericidal inhibitors of cell wall synthesis
-Inhibition of membrane binding proteins
-Inhibit transpeptidation rxn involved in cross linking
-Results in activation of autolytic enzymes
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-Strep
-Pneumococci
-Meningococci
-Treponema pallidum
PCN V:
-strep
-Oral pathogens
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-PCNases break lactam ring structures
-Structural changes in PBPs
-Adverse effects include hypersensitivity, Jarish-Herxheimer rxn in treatment of syphilis, maculopapular rash, interstitial nephritis
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Beta lactams- Narrow Spectrum and B lactamase resistant
-Nafcillin
-Methicillin
-Oxacillin
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-Same as above
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-Known or suspected staphylococci but not MRSA
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Beta lactams- Susceptible and wider spectrum
-Ampicillin
-Amoxicillin
-Ticaricillin
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-Same as above
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-Gram positive cocci (not staph)
-E coli
-Listeria monocytogenes (ampicillin)
-H. pylori
-Ticaricillin has extended activity against gram negative rods including pseudomonas
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-Synergy with aminoglycosides versus enterococci
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Cephalosporins, first generation
-Cephalexin
-Cephradine
-Cefazolin
If fourth letter is a consonant, it is a third generation this guy is bored
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-Bactericidal, identical to PCN in terms of mechanism of action
-Do not penetrate CNS please don’t use these for meningitis
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-G+ cocci
-E coli
-Klebsiella
-Proteus
(PECK)
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-Resistance occurs mainly via production of beta lactamases
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Cephalosporins, second generation
-Cefaclor
-Cefotetan
Organisms not covered by cephalosporins are LAME
(Listeria, Atypicals, MRSA, enterococcus)
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-Same as above
-Mostly do not penetrate CNS
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-More gram negative
-B. fragilis (cefotetan)
-H. flu
-Moraxella catarrhalis
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-Hypersensitivity
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Cephalosporins, third generation
-Ceftriaxone
-Cefixime
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-Wider spectrum cephalosporins. These drugs (most) enter the CNS. Important in empiric management of meningitis and sepsis
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-More gram negative
-N. gonorrhea
-B. fragilis (ceftizoxime)
-HENPECK
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-Hypersensitivity
-Most cleared renally
-Blocked by probenecid
-These drugs are weak acids, filtered and secreted in the kidney
-Ceftriaxone is handled by BILIARY clearance, no need to adjust dose in renal failure
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Cephalosporins , fourth generation
-Cefipeme
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-Same as above
-Resistant to beta lactamases
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-Broader spectrum
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Other inhibitors of cell wall synthesis
-Imipenem
-Meropenem
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-Carbapenem abx that are bactericidal and bind to PBPs. Same MOA as PCN and cephalosporins.
-Resistant to beta lactamases
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-Gram + cocci
-Gram negative rods
-Enterobacter, pseudomonas
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-GI distress
-Drug fever
DO NOT EFFECTIVELY TREAT: VRE, MRSA
-Impenem is given with cilastatin which inhibits metabolism by renal dihydropeptidases. Decrease dose in renal dyfunction
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