Microbiology- Antimicrobials Flashcards
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.