Antibiotics for micro final Flashcards
Penicillin G, V
Prototype β-lactam antibiotics (penicillinase-sensitive)
- Penicilling G → IV and IM form
- Penicillin V → oral
Penicillin G, V mechanism
- Bind penicillin-binding proteins (transpeptidases).
- Block transpeptidase cross-linking of peptidoglycan in cell wall.
- Activate autolytic enzymes.
Penicillin G,V clinical use
- Mostly used for gram-positive organisms
- S. pneumoniae
- S. pyogenes
- Actinomyces
- Gram negative cocci
- N. meningitidis
- Spirochetes
- T. pallidum
Bactericidal for gram-positive cocci, gram-positive rods, gram-negative cocci, and spirochetes.
Penicillinase sensitive.
Penicillin G, V toxicity
- Hypersensitivity reactions
- Hemolytic anemia
Penicillin G, V resistance
Penicillinase in bacteria (a type of β-lactamase) cleaves β-lactam ring.
Aminopenicillins
- amoxicillin
- ampicllin
Penicillinase-sensitive penicillins
Aminopenicillin mechanism
(and bioavailability)
- Same as penicillin → wider spectrum,
- Penicillinase sensitive.
- Also combine with clavulanic acid to protect against destruction by β-lactamase.
(amoxicillin and ampicillin)
Note that amoxicillin has greater oral bioavailability than ampicllin.
Aminopenicillin clinical use
Exteneded spectrum penicillin
- H. influenzae (gram negative)
- H. pylori (gram negative, oxidase positive, comma shaped)
- E. coli (gram negative rod)
- Listeria monocytogenes (gram positive rod)
- Proteus mirabilis (gram negative rod)
- Salmonella (gram negative rod)
- Shigella (gram negative rod)
- enterococci (gram positive cocci)
Aminopenicillin toxicity
- hypersensitivity reactions
- rash
- pseudomembranous colitis (ie C. dif, a gram positive rod)
Aminopenicillin resistance
Penicillinase in bacteria (a type of β-lactamase) cleaves β-lactam ring.
Penicillinase-resistant penicillins
- Dicloxacillin
- Nafcillin
- Oxacillin
Penicillinase resistant penicillins mechanism
(dicloxacillin, nafcillin, oxacillin)
Same as penicillin → narrow spectrum.
Penicillinase resistant because bulky R group blocks access of β-lactamase to β-lactam ring.
Penicillinase resistant penicillins clinical use
(dicloxacillin, nafcillin, oxacillin)
S. aureus (except MRSA; resistant because of altered penicillin-binding protein target site).
Penicillinase resistant penicillins toxicity
- Hypersensitivity reactions
- interstitial nephritis
Antipseudomonals
- Piperacillin
- Ticarcillin
Antipseudomonal mechanism
(piperacillin, ticarcillin)
Same as penicillin. Extended spectrum.
Antipseudomonal clinical use
(piperacillin, ticarcillin)
Pseudomonas spp. and other gram-negative rods.
Susceptible to penicillinase; use with β-lactamase inhibitors.
Antipseudomonal toxicity
(piperacillin, ticarcillin)
Hypersensitivity reactions.
Beta lactamase inhibitors
- Clavulanic Acid
- Sulbactam
- Tazobactam
Often added to penicillin antibiotics to protect the antibiotic from destruction by β-lactamase (penicillinase).
Cephalosporins (generations 1-4) mechanism
[and what don’t they cover]
β-lactam drugs that inhibit cell wall synthesis but are less susceptible to penicillinases. Bactericidal.
Organisms typically not covered by cephalosporins are LAME:
- Listeria
- Atypicals (Chlamydia, Mycoplasma)
- MRSA
- Enterococci
Exception: ceftaroline covers MRSA.
First generation cephalosporins
- Cefazolin (IV)
- cephalexin (oral)
First generation cephalosporin clinical use
1st generation (cefazolin, cephalexin)—
- gram-positive cocci
- gram-negative rods
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae
Cefazolin used prior to surgery to prevent S. aureus wound infections.
Second generation cephalosporins
- cefoxitin (IV)
- cefaclor
- cefuroxime
Second generation cephalosporin clinical use
2nd generation (cefoxitin, cefaclor, cefuroxime)—
- gram-positive cocci
- Haemophilus influenzae
- Enterobacter aerogenes
- Neisseria spp.
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae
- Serratia marcescens
Third generation cephalosporins
- ceftriaxone
- cefotaxime
- ceftazidime
Third generation cephalosporin clinical use
3rd generation (ceftriaxone, cefotaxime, ceftazidime)—serious gram-negative infections resistant to other β-lactams.
Ceftriaxone—meningitis, gonorrhea, disseminated Lyme disease (borrelia).
Ceftazidime—Pseudomonas
Fourth generation cephalosporins
cefepime
Fourth generation cephalosporin clinical use
4th generation (cefepime)—
gram-negative organisms
with ↑ activity against Pseudomonas and gram-positive organisms.
Fifth generation cephalosporins
Ceftaroline
Fifth generation cephalosporin clinical use
5th generation (ceftaroline)— broad gram-positive and gram-negative organism coverage, including MRSA.
Does not cover Pseudomonas.
Cephalosporin toxicity
- hypersensitivity reactions
- autoimmune hemolytic anemia
- disulfiram-like reaction
- vitamin K deficiency
- Exhibit cross-reactivity with penicillins, ↑ nephrotoxicity of aminoglycosides.
Cephalosporin resistance
Structural change in penicillin-binding proteins (transpeptidases).
Carbapenems
- imipenem
- meropenem
- ertapenem (limited Pseudomonas coverage)
- doripenem
Carbapenem mechanism
Imipenem is a broad-spectrum, β-lactamase–resistant carbapenem. Always administered with cilastatin (inhibitor of renal dehydropeptidase I) to ↓ inactivation of drug in renal tubules.
Carbapenem clnical use
(imipenem, meropenem, ertapenem, doripenem)
- Gram-positive cocci
- Gram-negative rods
- Anaerobes
Wide spectrum, but significant side effects limit use to life-threatening infections or after other drugs have failed.
Meropenem has a ↓ risk of seizures and is stable to dehydropeptidase I.
Carbapenem toxicity
- GI distress
- skin rash
- CNS toxicity (seizures) at high plasma levels
Monobactams
Aztreonam
Monobactam mechanism
Prevents peptidoglycan cross-linking by binding to penicillin- binding protein 3.
- Less susceptible to β-lactamases.
- Synergistic with aminoglycosides.
- No cross-allergenicity with penicillins.
Monobactam clinical use
Gram-negative rods only—no activity against gram-positives or anaerobes.
For penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides.
Monobactam toxicity
Usually nontoxic; occasional GI upset.
Glycopeptides
- Bacitracin
- Vancomycin