- Abscesses and Furuncles: A cutaneous abscess is a localized collection of pus. For small abscesses, the primary management is incision and drainage (I&D). Antibiotics may be added if the infection is moderate-to-severe or if there are systemic signs.
- Impetigo: This superficial infection is characterized by honey-colored crusting.
- Treatment: Mild cases are treated topically with mupirocin (preferred) or fusidic acid for 5 days. Moderate-to-severe cases may require oral cephalexin or clindamycin.
- Bacterial Folliculitis: This involves inflammation of the hair follicles. Management includes topical antimicrobial cleansers (e.g., benzoyl peroxide) or topical mupirocin.
Exam Tip: Differentiating MRSA
When treating purulent infections, consider Community-Acquired MRSA (CA-MRSA) coverage (e.g., TMP-SMX, Doxycycline, or Clindamycin) if the patient has specific risk factors, such as recent hospitalization, incarceration, or if the infection fails to respond to standard anti-MSSA/anti-streptococcal therapy.
Complicated SSTIs
Complicated infections involve deep structures like fascia and muscle, or occur in high-risk areas like the perianal region or diabetic foot ulcers.
- Animal and Human Bites: These are often polymicrobial, requiring coverage for both aerobes and anaerobes. Amoxicillin/clavulanate is a preferred oral option to target pathogens like Pasteurella spp..
- Necrotizing Infections: These are life-threatening emergencies characterized by rapid tissue necrosis and systemic toxicity, requiring immediate surgical debridement and broad-spectrum antibiotics.
Osteomyelitis
Osteomyelitis is the inflammation of the bone marrow and surrounding bone. It is categorized by its mechanism of infection and its duration (acute vs. chronic).
Mechanisms and Pathogens
The causative organisms vary significantly based on how the infection reached the bone:
- Hematogenous Osteomyelitis: Spread via the bloodstream. It is often monomicrobial, with Staphylococcus aureus being the most common pathogen across most age groups.
- Contiguous Osteomyelitis: Spreads from an adjacent site of infection, such as a poorly healing soft tissue wound or trauma. These are often polymicrobial.
- Vascular Insufficiency Osteomyelitis: Common in patients with diabetes or peripheral vascular disease, where tissue is open to the environment (e.g., diabetic foot ulcers). These are also frequently polymicrobial.
Management of Osteomyelitis
Pharmacological Therapy
Treatment for osteomyelitis is prolonged, typically requiring at least 6 weeks of antibiotic therapy.
- Initial Parenteral Therapy: Patients often begin with IV antibiotics based on suspected pathogens:
- MSSA: Cefazolin or Ceftriaxone.
- MRSA: Vancomycin, Daptomycin, or Linezolid.
- Anaerobes: Clindamycin or Metronidazole.
- Oral Stepdown: Transitioning from IV to oral (PO) therapy is a critical step. This can be considered when the patient is clinically improving, no further surgery is anticipated, and cultures are available to guide definitive management. Effective oral options include fluoroquinolones, clindamycin, doxycycline (with rifampin), TMP-SMX, and linezolid.
Non-Pharmacological Measures
Antibiotics alone are often insufficient for bone infections; mechanical and supportive measures are essential:
- Surgical Decompression and Debridement: To remove necrotic bone and infected soft tissue, which improves antibiotic penetration.
- Wound Care: Regular dressing changes and monitoring for infection progression.
- Pressure Offloading: Essential for patients with diabetic foot ulcers or pressure injuries to reduce ongoing tissue damage.
- Revascularization: Improving blood flow is vital to enhance both healing and the delivery of systemic antibiotics to the site of infection.
Monitoring Parameters
Monitoring is divided into assessing whether the treatment is working (efficacy) and ensuring the treatment is not causing harm (safety).
Efficacy Endpoints
Clinicians should look for a reduction in the signs and symptoms of infection (e.g., decreased redness, swelling, and pain). For SSTIs, improvement is typically expected within 5 days. For osteomyelitis, monitoring involves tracking a downward trend in inflammatory markers, specifically C-reactive protein (CRP) and Erythrocyte Sedimentation Rate (ESR), over the course of treatment. Routine imaging is not standard for monitoring unless there is clinical suspicion of treatment failure.
Safety Endpoints
Monitoring must include the assessment of adverse drug reactions and complications throughout the duration of the therapy.
