Antibiotic Basics

Beta-Lactams

* Penicillin

• • Strep Pharyngitis (including scarlet fever) Streptococcal Toxic Shock and Necrotizing Fascitis
    • Penicillin plus clindamycin (to decrease toxin synthesis)
  • Meningococcus Meningitis
  • Syphilis (Primary, 2ndary, and latent syphilis < 1 year duration)
  • Actinomycosis
  • Anthrax
  • Clostridial infections
  • Listeria
  • Pasteurella
• Penicilinase-Resistant Penicillins
  • Nafcillin, oxacillin, dicloxacillin
    • Agents of 1st choice for treatment of S. aureus and S. epidermidis that are not methicillin-reistant

* Expanded-Spectrum Penicillins

• • Ampicillin, amoxicillin (+ clavulanate)
    • Upper Respiratory Infections (due to S. pyogenes, S. pneumoniae, H. influenzae)
      • Sinusitis
      • Otitis media
      • Acute exacerbation of chronic bronchitis
    • Listeria
• Antipseudomonal Penicillins
  • Piperacillin
    • Infection following burns
    • Neutropenia

* 1st Gen Cephalosporins

• • Cefazolin, cephalexin
    • Skin and soft tissue infections (why is agent of choice before gen sx)
  • Cross-reactivity of PCN allergy <10%

* 2nd Gen Cephalosporins

• • Cefuroxime
    • Intestinal anaerobes (why is agent of chioce for colorectal sx)
    • Largely displaced by 3rd gen agents
• 3rd Gen Cephalosporins
  • Ceftriaxone, Ceftazidime, Cefixime
    • Drug of choice for serious infections due to:
      • Klebsiella
      • Enterobacter
      • Proteus
      • Haemophilus
    • Gonorrhea
    • Lyme disease
    • Meningitis (+ vanc and ampicillin)
    • Pseudomonas meningitis (+ AG)
• 4th Gen Cephalosporins
  • Cefepime
    • Resistant, nosocomial infections
• Carbapenems
  • Imipenem (+ cilastatin), meropenem
    • Cephalosporin-resistant nosocomial bacteria
    • Empirical treatment of serious infections in patients who recently received other b-lactams
• Aztreonam
  • Antimicrobial activity more closely resembles AG's (only active against gram -)
    • Enterobacter, pseudomonas, H. influenzae, gonococci
    • Little allergic cross-reactivity with B-lactam antibiotics

Aminoglycosides

• Gentamicin, amikacin, streptomycin (either alone or with B-lactam)
  • Serious gram-negative bacillary infections
    • Ill patient with pyelonephritis
    • Meningitis (due to Pseudomonas, Acinetobacter)
    • Peritoneal Dialysis–Associated Peritonitis
    • Bacterial endocarditis?
• Caution: Use in patients with Myasthenia Gravis, can precipitate crisis

Sulfonamides

• Trimethoprim-sulfamethoxazole
  • 1st line for uncomplicated lower UTI (especially chronic and recurrent infections)
  • PCP pneumonia
  • Acute exacerbations of chronic bronchitis
  • Maxillary sinusitis

Fluoroquinolones

• UTI (2nd line)
• Prostatitis
• Chlamydia
• PID
• Traveler's diarrhea

Tetracyclines

• Mycoplasma
• Chlamydia
• PID (combined with cephalosporin)
• Epididymitis
• Anthrax

Macrolides

• Erythromycin, Clarithromycin, Azithromycin
  • Community-acquired PNA
  • Mycoplasma
  • Legionnaires' Disease
  • Chlamydia (single dose)
  • H. Pylori
  • Traveler's diarrhea (children and pregnant women)

Clindamycin

• Drug of choice for lung abscess and anaerobic lung and pleural space infections
• Toxin-mediated disease, i.e. toxic shock syndrome (TSS)

See Also

• Antibiotics (Main)

Source

Goodman & Gilman's Pharmacology