💊 Infectious Disease Guide Pro

Evidence-Based Antimicrobial Prescribing by Didactic Med

🎯 Quick Reference Guide

  • ✅ First-line treatments highlighted in green
  • ⚠️ Alternative treatments highlighted in yellow
  • 📋 Click infection names to expand treatment details
  • 💾 Use medication drawer to save frequently used drugs
  • 📚 Evidence links provided for all recommendations

🚨 Empiric Therapy Principles

▼
Local Antibiogram
Always consult your institution's antibiogram for resistance patterns
De-escalation
Narrow spectrum once culture results available
Renal Adjustment
Adjust doses for CrCl < 50 mL/min for most antibiotics

🫁 Respiratory Infections

Community-Acquired Pneumonia (CAP)

S. pneumoniae, atypicals
Amoxicillin + Azithromycin
Amoxicillin: 1g PO TID
Azithromycin: 500mg day 1, then 250mg daily
Duration: 5-7 days
Levofloxacin (monotherapy)
750mg PO/IV daily
Duration: 5 days
Ceftriaxone + Azithromycin
Ceftriaxone: 1-2g IV daily
Azithromycin: 500mg IV daily
Duration: 5-7 days
Severe CAP (ICU): Ceftriaxone 2g IV daily + Azithromycin 500mg IV daily
IDSA Guidelines 2019

Acute Bacterial Sinusitis

S. pneumoniae, H. influenzae
Amoxicillin-Clavulanate
875/125mg PO BID or 2000/125mg PO BID (XR)
Duration: 5-7 days (adults)
Doxycycline
100mg PO BID or 200mg PO daily
Duration: 5-7 days
Levofloxacin
500mg PO daily
Duration: 5 days
Penicillin Allergy: Doxycycline or Levofloxacin preferred
IDSA Guidelines 2012

Group A Strep Pharyngitis

S. pyogenes
Penicillin V
500mg PO BID-TID
Duration: 10 days
Amoxicillin
500mg PO BID or 1000mg PO daily
Duration: 10 days
Azithromycin (Penicillin allergy)
500mg day 1, then 250mg daily
Duration: 5 days total
Cephalexin
500mg PO BID
Duration: 10 days
IDSA Guidelines 2012

🧠 Central Nervous System Infections

Bacterial Meningitis (Empiric)

S. pneumoniae, N. meningitidis
Ceftriaxone + Vancomycin
Ceftriaxone: 2g IV q12h
Vancomycin: 15-20mg/kg IV q8-12h
Duration: 10-14 days
+ Dexamethasone
0.15mg/kg IV q6h x 2-4 days
Give before or with first antibiotic dose
Age > 50 or immunocompromised: Add Ampicillin 2g IV q4h for Listeria coverage

⚠️ Critical Points

  • Start antibiotics immediately - do not delay for LP
  • Dexamethasone most beneficial for S. pneumoniae
  • Adjust vancomycin to achieve trough 15-20 mcg/mL
IDSA Guidelines 2004

Herpes Simplex Encephalitis

HSV-1, HSV-2
Acyclovir IV
10mg/kg IV q8h
Duration: 14-21 days

⚠️ Important

  • Start empirically if suspected - do not wait for PCR
  • Ensure adequate hydration to prevent nephrotoxicity
  • Consider repeat LP if no improvement after 72h

❤️ Cardiovascular Infections

Native Valve Endocarditis (Empiric)

S. aureus, Streptococci
Vancomycin + Ceftriaxone
Vancomycin: 15-20mg/kg IV q12h
Ceftriaxone: 2g IV daily
Duration: 4-6 weeks
MSSA (once confirmed): Nafcillin 2g IV q4h or Cefazolin 2g IV q8h
Enterococcal: Ampicillin 2g IV q4h + Gentamicin 1mg/kg IV q8h
AHA/IDSA Guidelines 2015

🔄 Gastrointestinal Infections

Clostridioides difficile Infection

C. difficile
Fidaxomicin
200mg PO BID
Duration: 10 days
Vancomycin (oral)
125mg PO QID
Duration: 10 days
Metronidazole (mild cases only)
500mg PO TID
Duration: 10 days
Fulminant: Vancomycin 500mg PO QID + Metronidazole 500mg IV q8h
Recurrent (1st): Fidaxomicin 200mg PO BID x 10d or Vancomycin taper
IDSA/SHEA Guidelines 2021

Traveler's Diarrhea

ETEC, Campylobacter, Shigella
Azithromycin
1000mg PO x 1 dose or 500mg PO daily x 3 days
Duration: 1-3 days
Ciprofloxacin
500mg PO BID
Duration: 1-3 days
Rifaximin
200mg PO TID
Duration: 3 days
SE Asia travel: Azithromycin preferred (FQ resistance common)

Diverticulitis

E. coli, Bacteroides
Amoxicillin-Clavulanate
875/125mg PO BID
Duration: 4-7 days
Ciprofloxacin + Metronidazole
Cipro: 500mg PO BID
Metronidazole: 500mg PO TID
Duration: 4-7 days
TMP-SMX + Metronidazole
TMP-SMX: 1 DS tab PO BID
Metronidazole: 500mg PO TID
Duration: 4-7 days
Complicated: Piperacillin-tazobactam 3.375g IV q6h or Ceftriaxone 1g IV daily + Metronidazole 500mg IV q8h

🩸 Bloodstream/Systemic Infections

MRSA Bacteremia

Methicillin-resistant S. aureus
Vancomycin
15-20mg/kg IV q8-12h (target trough 15-20)
Duration: Minimum 2 weeks (uncomplicated)
Daptomycin
8-10mg/kg IV daily
Duration: Minimum 2 weeks

⚠️ Critical Management

  • Remove all lines/hardware if possible
  • Echo to rule out endocarditis
  • Repeat blood cultures 48-72h
  • 4-6 weeks if complicated

Lyme Disease

Borrelia burgdorferi
Doxycycline (Early localized)
100mg PO BID
Duration: 10-14 days (21 days for early disseminated)
Amoxicillin
500mg PO TID
Duration: 14-21 days
Ceftriaxone (Neurologic)
2g IV daily
Duration: 14-28 days
Carditis: Ceftriaxone 2g IV daily x 14-21 days
Arthritis: Doxycycline 100mg PO BID x 28 days
IDSA Guidelines 2020

🦴 Skin & Soft Tissue Infections

Cellulitis (Non-purulent)

Group A Strep, S. aureus
Cephalexin
500mg PO QID
Duration: 5-10 days
Dicloxacillin
500mg PO QID
Duration: 5-10 days
Clindamycin
300-450mg PO TID-QID
Duration: 5-10 days
MRSA risk: Add TMP-SMX DS 1-2 tabs PO BID or Doxycycline 100mg PO BID
IDSA Guidelines 2014

Abscess/Purulent Cellulitis

MRSA, MSSA
TMP-SMX DS
1-2 tabs PO BID
Duration: 5-10 days
Doxycycline
100mg PO BID
Duration: 5-10 days
Clindamycin
300-450mg PO TID
Duration: 5-10 days

⚠️ Remember

  • I&D is primary treatment for abscesses
  • Antibiotics indicated if >2cm, multiple lesions, or systemic symptoms

Necrotizing Fasciitis

Group A Strep, polymicrobial
Piperacillin-tazobactam + Vancomycin + Clindamycin
Pip-tazo: 3.375g IV q6h
Vancomycin: 15-20mg/kg IV q12h
Clindamycin: 600-900mg IV q8h
Surgical emergency - immediate debridement required

🚨 EMERGENCY

  • Immediate surgical consultation
  • Clindamycin for toxin suppression
  • Consider IVIG for streptococcal toxic shock

🚽 Genitourinary Infections

Uncomplicated Cystitis

E. coli, Klebsiella
Nitrofurantoin
100mg PO BID
Duration: 5 days
TMP-SMX DS
1 tab PO BID
Duration: 3 days
Fosfomycin
3g PO x 1 dose
Single dose
Ciprofloxacin
250mg PO BID
Duration: 3 days
Pregnancy: Cephalexin 500mg PO QID x 7 days or Amoxicillin-clavulanate 500mg PO BID x 7 days
IDSA Guidelines 2019

Pyelonephritis

E. coli, Proteus
Ciprofloxacin
500mg PO BID or 400mg IV q12h
Duration: 7 days (PO) or 14 days total
Levofloxacin
750mg PO/IV daily
Duration: 5-7 days
Ceftriaxone
1g IV/IM daily
Duration: 10-14 days
Severe/Septic: Ceftriaxone 1g IV daily until afebrile, then oral step-down

Gonorrhea/Chlamydia

N. gonorrhoeae, C. trachomatis
Ceftriaxone + Doxycycline
Ceftriaxone: 500mg IM x 1 (1g if ≥150kg)
Doxycycline: 100mg PO BID x 7 days
Treats both infections
Gentamicin + Azithromycin
Gentamicin: 240mg IM x 1
Azithromycin: 2g PO x 1
For ceftriaxone allergy
Pregnancy (Chlamydia): Azithromycin 1g PO x 1
CDC STI Guidelines 2021

Syphilis

Treponema pallidum
Benzathine Penicillin G (Primary/Secondary)
2.4 million units IM x 1
Single dose
Benzathine Penicillin G (Late latent)
2.4 million units IM weekly x 3
3 weeks total
Doxycycline (Penicillin allergy)
100mg PO BID
14 days (primary) or 28 days (late)
Neurosyphilis: Aqueous Penicillin G 3-4 million units IV q4h x 10-14 days

🦴 Bone & Joint Infections

Osteomyelitis

S. aureus most common
Nafcillin/Oxacillin (MSSA)
2g IV q4h
Duration: 4-6 weeks
Cefazolin (MSSA)
2g IV q8h
Duration: 4-6 weeks
Vancomycin (MRSA)
15-20mg/kg IV q12h
Duration: 4-6 weeks
Oral step-down options:
MSSA: Cephalexin 1g PO QID or Levofloxacin 750mg PO daily
MRSA: TMP-SMX DS 2 tabs PO BID + Rifampin 600mg PO daily
IDSA Guidelines 2015

Septic Arthritis

S. aureus, N. gonorrhoeae
Vancomycin + Ceftriaxone
Vancomycin: 15-20mg/kg IV q12h
Ceftriaxone: 1-2g IV daily
Duration: 2-4 weeks

⚠️ Management

  • Urgent arthrocentesis and drainage
  • Consider orthopedic consultation
  • Narrow therapy based on cultures
Gonococcal: Ceftriaxone 1g IV/IM daily x 7-14 days

📋 Medication Quick Reference

Common Renal Adjustments

  • Vancomycin: Adjust for CrCl <50
  • Pip-tazo: 2.25g q6h if CrCl 20-40
  • Levofloxacin: 750mg q48h if CrCl 20-49
  • TMP-SMX: Avoid if CrCl <15
  • Nitrofurantoin: Avoid if CrCl <60

Allergy Alternatives

  • Penicillin allergy: Azithromycin, Doxycycline, FQ
  • Sulfa allergy: Avoid TMP-SMX
  • Beta-lactam: Consider Aztreonam for gram-negatives