IDSA Guidelines for Treating Infections
The Infectious Diseases Society of America (IDSA) provides comprehensive, evidence-based guidelines for the diagnosis and management of various infectious diseases, with specific recommendations tailored to different infection types, patient populations, and clinical scenarios.
Skin and Soft Tissue Infections (SSTIs)
Classification and Diagnosis
- IDSA classifies SSTIs into purulent (abscesses, furuncles, carbuncles) and non-purulent (cellulitis, erysipelas) infections 1
- Severity is categorized as mild, moderate, or severe based on:
- Systemic signs (temperature >38°C, heart rate >90 beats/min, respiratory rate >24 breaths/min)
- Abnormal white blood cell count (<12,000 or <400 cells/μL)
- Immunocompromised status
- Presence of deeper infection signs (bullae, skin sloughing, hypotension)
Treatment Recommendations
Purulent infections:
- Mild: Incision and drainage alone is the primary treatment
- Moderate: Incision and drainage plus oral antibiotics active against MRSA
- Severe: Hospitalization and parenteral antibiotics (vancomycin, daptomycin, linezolid, etc.)
Non-purulent infections:
- Mild: Oral antibiotics targeting streptococci
- Moderate: Oral or parenteral antibiotics
- Severe: Parenteral antibiotics with broad coverage
Special Considerations
- For anaerobic infections in wounds, particularly in patients with ischemia or deep tissue involvement, empiric antibiotic therapy should include anaerobic coverage 2
- For specific pathogens:
- Vibrio vulnificus: Doxycycline plus ceftazidime
- Aeromonas hydrophila: Doxycycline plus ciprofloxacin
- Polymicrobial: Vancomycin plus piperacillin/tazobactam 1
Clostridioides difficile Infection (CDI)
Treatment Recommendations
Initial CDI episode:
- Preferred: Fidaxomicin 200 mg twice daily for 10 days
- Alternative: Vancomycin 125 mg four times daily for 10 days
- For non-severe CDI if above agents unavailable: Metronidazole 500 mg three times daily for 10-14 days 1
First CDI recurrence:
- Preferred: Fidaxomicin 200 mg twice daily for 10 days, OR twice daily for 5 days followed by once every other day for 20 days
- Alternative: Vancomycin in a tapered and pulsed regimen
- Adjunctive treatment: Consider bezlotoxumab 10 mg/kg IV once during standard-of-care antibiotics 1
Second or subsequent CDI recurrence:
- Fidaxomicin regimen as above
- Vancomycin in a tapered and pulsed regimen
- Vancomycin followed by rifaximin
- Fecal microbiota transplantation (after at least 2 recurrences) 1
Fulminant CDI:
- Vancomycin 500 mg four times daily orally or via nasogastric tube
- Consider adding rectal instillation of vancomycin if ileus present
- IV metronidazole 500 mg every 8 hours should be administered together with oral/rectal vancomycin 1
Intra-abdominal Infections
Classification
- Community-acquired vs. healthcare-associated
- Primary, secondary (community-acquired and postoperative), and tertiary peritonitis 1
Microbiologic Considerations
- For community-acquired infections, the location of gastrointestinal perforation determines the infecting flora
- Microbiologic workup should focus on identification and susceptibility testing of facultative and aerobic gram-negative bacilli
- B. fragilis group isolates show substantial resistance to clindamycin, cefotetan, cefoxitin, and quinolones 1
Lyme Disease
Prevention
- Personal protective measures to reduce tick exposure
- Use of repellents: DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD, 2-undecanone, or permethrin
- Prompt removal of attached ticks using fine-tipped tweezers 1
Prophylaxis
- Single-dose doxycycline (200 mg for adults, 4.4 mg/kg up to 200 mg for children) within 72 hours of removing a high-risk tick bite
- High-risk tick bite defined as: identified Ixodes spp. vector, highly endemic area, and tick attached for ≥36 hours 1
Treatment
- Erythema migrans: 10-day course of doxycycline or 14-day course of amoxicillin or cefuroxime axetil 1
Intravascular Catheter-Related Infections
Management Principles
- Management varies according to catheter type
- After appropriate cultures, empirical IV antimicrobial therapy should be initiated based on clinical presentation, severity, underlying disease, and potential pathogens
- For non-tunneled CVC-related bacteremia and fungemia, the CVC should generally be removed
- For tunneled catheter or implantable device infections, removal decision depends on illness severity, documented infection, pathogen, and complications 1
Key Principles Across Guidelines
Evidence-based approach: IDSA guidelines use standardized methodology for rating evidence quality and recommendation strength, typically using the GRADE system
Patient-centered care: Guidelines recognize individual variation among patients and emphasize physician judgment in specific clinical situations
Antimicrobial stewardship: Recommendations focus on appropriate antibiotic selection, duration, and de-escalation when possible
Regular updates: Guidelines are periodically reviewed and updated to incorporate new evidence and emerging pathogens
Common Pitfalls to Avoid
- Underestimating infection severity, especially in immunocompromised patients
- Failing to obtain appropriate cultures before initiating antibiotics
- Using broad-spectrum antibiotics when narrow-spectrum would suffice
- Not considering local antimicrobial resistance patterns
- Inadequate source control (e.g., drainage of abscesses, removal of infected devices)
- Overlooking the need for surgical consultation in severe infections
By following these evidence-based guidelines while considering individual patient factors and local resistance patterns, clinicians can optimize the management of infectious diseases and improve patient outcomes.