Infections / Antibiotics


  1. In patients with a suspected infection,
    1. Determine the correct tools (e.g., swabs, culture/transport medium), techniques, and protocols for cultures,
    2. Culture when appropriate (e.g., throat swabs/sore throat guidelines).
  2. When considering treatment of an infection with an antibiotic, do so
    1. Judiciously (e.g., delayed treatment in otitis media with comorbid illness in acute bronchitis),
    2. Rationally (e.g., cost, guidelines, comorbidity, local resistance patterns).
  3. Treat infections empirically when appropriate (e.g., in life threatening sepsis without culture report or confirmed diagnosis, candida vaginitis post-antibiotic use).
  4. Look for infection as a possible cause in a patient with an ill defined problem (e.g., confusion in the elderly, failure to thrive, unexplained pain [necrotizing fasciitis, abdominal pain in children with pneumonia]).
  5. When a patient returns after an original diagnosis of a simple infection and is deteriorating or not responding to treatment, think about and look for more complex infection. (i.e., When a patient returns complaining they are not getting better, don’t assume the infection is just slow to resolve).
  6. When treating infections with antibiotics use other therapies when appropriate (e.g., aggressive fluid resuscitation in septic shock, incision and drainage abscess, pain relief).


  1. In patients requiring antibiotic therapy, make rational choices (i.e., first-line therapies, knowledge of local resistance patterns, patient’s medical and drug history, patient’s context).
  2. In patients with a clinical presentation suggestive of a viral infection, avoid prescribing antibiotics.
  3. In a patient with a purported antibiotic allergy, rule out other causes (e.g., intolerance to side effects, non-allergic rash) before accepting the diagnosis.
  4. Use a selective approach in ordering cultures before initiating antibiotic therapy (usually not in uncomplicated cellulitis, pneumonia, urinary tract infections, and abscesses; usually for assessing community resistance patterns, in patients with systemic symptoms, and in immunocompromised patients).
  5. In urgent situations (e.g., cases of meningitis, septic shock, febrile neutropenia), do not delay administration of antibiotic therapy (i.e., do not wait for confirmation of the diagnosis)

Example First-Line Therapies

  • Base on local resistance patterns, patient's medical and recent antibiotic history

Urinary Tract Infection

  • Women/Pregnant: Nitrofurantoin 100mg PO BID x 5-7d
  • Man/Complicated/Pyelonephritis: Ciprofloxacin 500mg PO BID x 7d
  • Pediatrics: Amoxicillin 50 mg/kg/day PO ÷ TID x 5d afebrile, 10d febrile
    • Complicated: Cefixime 16mg/kg first day, then 8mg/kg daily

Uncomplicated Cellulitis (no MRSA coverage)

  • Adult: Cefadroxil 1g PO daily (or BID) x 5-14d
  • Pediatrics: Cephalexin 50-100mg/kg/d ÷ QID x 10-14d


Acute Otitis Media

  • Adult: Amoxicillin 500mg PO TID x 5-7d
  • Pediatrics: Amoxicillin 90 mg/kg/day PO ÷ BID x 5d-10d (10d if <2yo or severe symptoms)

Otitis externa

  • Ciprodex otic suspension 4 drops BID x 5d

Strep Pharyngitis

  • Adult: Penicillin V 600mg PO BID x 10d
  • Pediatrics: Amoxicillin 50 mg/kg PO daily (max 1g/day) x 10d

Community Acquired Pneumonia

  • Adult: Clarithromycin 500mg PO BID x 7d (or Amoxicillin 1g PO TID x7d if do not need to cover atypicals)
  • Pediatrics: Amoxicillin 90mg/kg/day (max 3g/day) ÷ TID x 7-10d

Acute Rhinosinusitis

  • Adult: Amoxicillin 500mg PO TID x 5-10d
  • Pediatrics: Amoxicillin 90mg/kg/day (max 2g/day) ÷ BID x 10-14d
  • Second-line or if suspect resistance (S pneumo) Amox/Clav 40-80mg/kg/day ÷ BID (or 875/125 mg PO BID)


Bacterial Vaginosis

  • Metronidazole 500mg PO BID x 7d

Herpes Simplex Virus

  • First episode Acyclovir 400mg PO TID x 7-10d
  • Recurrent Episode: Acyclovir 400mg PO TID x 5d (or 800mg PO TID x 2d)


  • Ceftriaxone 250mg IM or Cefixime 800mg PO x1 + Azithromycin 1g PO x1 or Doxycycline 100mg PO BID x 7d


Moderate-Severe Gastroenteritis (>3BM/d, blood, fever)

  • Consider Cipro 500mg PO BID x 3 days or 750mg PO x1
  • Consider Azithromycin 1g PO x1 if travel to Asia (resistance to fluoroquinolones)

C-difficile Colitis

  • Vancomycin 125mg PO QID x 10-14d
  • Pediatrics: 40mg/kg/d PO (max 2g/d) ÷ TID-QID x 10-14d

Peptic Ulcer Disease (non-NSAID related)

  • PPI PO BID + Amoxicillin 1g PO BID + Clarithromycin 500mg PO BID x14d (eg. HP-PAC)
    • Second-line or if high resistance, add Metronidazole 500mg PO BID (CLAMET)

Antibiotic Rash

  • Stop antibiotic, and avoid further antibiotics until cleared
    • Unlikely true IgE-mediated allergy
      • IgE-independent reaction (eg. Red Man Syndrome with vancomycin)
      • Delayed T-cell reaction (usually concomitant viral infection, eg EBV)
    • Rule out
      • Serum Sickness (Type 3) - vasculitic rash, arthralgias, flu-like symptoms, fever
      • DRESS (fever, rash, lymphadenopathy, blood count abnormality [eosinophilia, thrombocytopenia])
      • SJS/TEN (desquamation, positive Nikolsky's sign, mucosal-involvement)
    • Referral to Allergy for challenge testing