Microbiology- Antimicrobials Flashcards
(43 cards)
Antimicrobial therapy Imagen
Pag. 187
Penicillin G, V
- Mechanism
- Clinical Use
Penicillin G (IV and IM form), penicillin V (oral). Prototype β-lactam antibiotics.
D-Ala-D-Ala structural analog. Bind penicillin-binding proteins (transpeptidases).
Mostly used for gram ⊕ organisms (S pneumoniae, S pyogenes, Actinomyces). Also used for gram ⊝ cocci (mainly N meningitidis) and spirochetes (namely T pallidum). Bactericidal for gram ⊕ cocci, gram ⊕ rods, gram ⊝ cocci, and spirochetes.
Penicillin G, V
- Adverse effects
- Resistance
Hypersensitivity reactions, direct Coombs ⊕ hemolytic anemia, drug-induced interstitial nephritis.
β-lactamase cleaves the β-lactam ring. Mutations in penicillin-binding proteins.
Penicillinase-sensitive penicillins
(Amoxicillin, ampicillin; aminopenicillins.)
- Mechanism
- Clinical Use
Same as penicillin. penicillinase sensitive. Also combine with clavulanic acid
“HHELPSS”
Extended-spectrum penicillin—H influenzae, H pylori, E coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella, enterococci.
*AmOxicillin has greater Oral bioavailability than ampicillin.
Penicillinase-sensitive penicillins
- Adverse effects
- Resistance
Hypersensitivity reactions, rash, pseudomembranous colitis.
Penicillinase (a type of β-lactamase) cleaves β-lactam ring.
Penicillinase-resistant penicillins (Dicloxacillin, nafcillin, oxacillin.) - Mechanism - Clinical Use - Adverse effects - Resistance
Same as penicillin.
S aureus (except MRSA).
Hypersensitivity reactions, interstitial nephritis.
MRSA has altered penicillin-binding protein target site.
Antipseudomonal penicillins (Piperacillin, ticarcillin) - Mechanism - Clinical Use - Adverse effects
Same as penicillin
Pseudomonas spp. and gram ⊝ rods.
Hypersensitivity reactions.
β-lactamase inhibitors
CAST.
Clavulanic acid, Avibactam, Sulbactam, Tazobactam.
Cephalosporins
- Mechanism
- Organisms not covered
- Adverse effects
- Resistance
β-lactam drugs that inhibit cell wall synthesis
LAME:
Listeria, Atypicals (Chlamydia, Mycoplasma), MRSA, and Enterococci.
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction, vitamin K deficiency. Low rate of crossreactivity even in penicillin-allergic patients. nephrotoxicity of aminoglycosides.
Inactivated by cephalosporinases. Structural change in penicillinbinding proteins (transpeptidases).
Cephalosporins 1st Generation
- Names
- Clinical use
cefazolin, cephalexin
PEcK.
gram ⊕ cocci, Proteus mirabilis, E coli, Klebsiella
pneumoniae. Cefazolin used prior to surgery to
prevent S aureus wound infections.
Cephalosporins 2nd Generation
- Names
- Clinical use
cefaclor, cefoxitin, cefuroxime, cefotetan
HENS PEcK.
gram ⊕ cocci, H influenzae, Enterobacter aerogenes, Neisseria spp., Serratia marcescens, Proteus mirabilis, E coli, Klebsiella pneumoniae.
Cephalosporins 3rd Generation
- Names
- Clinical use
ceftriaxone, cefotaxime, cefpodoxime, ceftazidime
serious gram ⊝ infections resistant to other β-lactams.
Ceftriaxone—meningitis, gonorrhea, disseminated Lyme disease.
Ceftazidime—Pseudomonas.
*Can cross blood-brain barrier.
Cephalosporins 4th Generation
- Names
- Clinical use
Cefepime
gram ⊝ organisms, with activity against Pseudomonas and gram ⊕ organisms.
Cephalosporins 5th Generation
- Names
- Clinical use
Ceftaroline
broad gram ⊕ and gram ⊝ organism coverage;
unlike 1st–4th generation cephalosporins, ceftaroline covers Listeria, MRSA, and Enterococcus faecalis—
does not cover Pseudomonas.
Carbapenems
- Names
- Mechanism
DIME
Doripenem, Imipenem, Meropenem, Ertapenem
Imipenem is a broad-spectrum, β-lactamase– resistant carbapenem. Always administered with cilastatin (inhibitor of renal dehydropeptidase I)
Newer carbapenems include ertapenem (limited
Pseudomonas coverage) and doripenem.
Carbapenems
- Clinical use
- Adverse effects
Gram ⊕ cocci, gram ⊝ rods, and anaerobes. limit use to life-threatening infections or after other drugs have failed.
Meropenem has a risk of seizures and is stable to
dehydropeptidase I.
GI distress, rash, and CNS toxicity (seizures) at high plasma levels.
Monobactams (Aztreonam)
- Mechanism
- Clinical use
- Adverse effects
Less susceptible to β-lactamases. Synergistic with aminoglycosides. No cross-allergenicity with penicillins.
Gram ⊝ rods only—no activity against gram ⊕ rods or anaerobes. For penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides.
Usually nontoxic; occasional GI upset.
Vancomycin
- Mechanism
- Clinical use
Inhibits cell wall peptidoglycan formation by binding D-Ala-D-Ala portion of cell wall precursors. Bactericidal against most bacteria (bacteriostatic against C difficile).
Gram ⊕ bugs only—serious, multidrug-resistant organisms, including MRSA, S epidermidis, sensitive Enterococcus species, and Clostridium difficile (oral dose for pseudomembranous colitis).
Vancomycin
- Adverse effects
- Resistance
NOT
Nephrotoxicity, Ototoxicity, Thrombophlebitis, diffuse flushing—red man syndrome (largely preventable by pretreatment with antihistamines and slow infusion rate), drug reaction with eosinophilia and systemic symptoms (DRESS syndrome).
(eg, Enterococcus) via amino acid modification of D-Ala-D-Ala to D-Ala-D-Lac.
Protein synthesis inhibitors
All are bacteriostatic, except aminoglycosides
(bactericidal) and linezolid (variable).
“Buy AT 30, CCEL (sell) at 50.”
30S inhibitors
Aminoglycosides
Tetracyclines
50S inhibitors
Chloramphenicol, Clindamycin
Erythromycin (macrolides)
Linezolid
Aminoglycosides
- Names
- Clinical uses
GNATS: Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin.
*Require O2 for uptake; therefore ineffective against anaerobes.
Severe gram ⊝ rod infections. Synergistic with β-lactam antibiotics. Neomycin for bowel surgery.
Aminoglycosides
- Adverse effects
- Resistance
Nephrotoxicity, Neuromuscular blockade, Ototoxicity (especially when used with loop diuretics). Teratogen.
Bacterial transferase enzymes inactivate the drug by acetylation, phosphorylation, or adenylation.
Tetracyclines
- Names
- Characteristics
- Clinical uses
Tetracycline, doxycycline, minocycline.
Limited CNS penetration. Doxycycline is fecally eliminated and can be used in patients with renal failure. Do not take
tetracyclines with milk (Ca2+), antacids (Ca2+ or Mg2+), or iron-containing preparations because divalent cations inhibit drugs’ absorption in the gut.
Borrelia burgdorferi, M pneumoniae. Drugs’ ability to accumulate intracellularly makes them very effective against Rickettsia and Chlamydia. Also used to treat acne. Doxycycline effective against MRSA.
Tetracyclines
- Adverse effects
- Resistance
GI distress, discoloration of teeth and inhibition of bone growth in children, photosensitivity. Contraindicated in pregnancy.
uptake or efflux out of bacterial cells by plasmid-encoded transport pumps.
