[Cellulitis and necrotizing fasciitis: microbiology and pathogenesis]

Area of Science:

• Infectious Diseases
• Microbiology
• Dermatology

Background:

• Streptococcus pyogenes and Staphylococcus aureus are significant pathogens causing necrotizing cutaneous infections.
• Bacterial surface components (e.g., Protein M, capsule) and toxins (e.g., streptolysin O, pyrogenic exotoxins, toxic shock syndrome toxin) mediate adherence, invasiveness, and tissue damage.
• These infections can be polymicrobial, involving various anaerobes and other bacteria depending on the infection site.

Framework:

• Understanding the pathogenic mechanisms of Streptococcus pyogenes and Staphylococcus aureus, including their virulence factors.
• Identifying common co-infecting microorganisms like anaerobes (Peptostreptococcus, Prevotella, Porphyromonas, Fusobacterium) and enterobacteria.
• Recognizing the role of superantigens in toxic shock syndrome.

Implementation:

• Penicillin is the primary treatment for streptococcal infections, but clindamycin or other protein synthesis inhibitors are recommended for severe cases.
• Initial therapy must address potential co-infections with Staphylococcus aureus and anaerobes.
• Broad-spectrum antibiotics may be necessary for infections involving enterobacteria.

Implications:

• Effective management requires prompt and aggressive surgical exploration and debridement of infected tissues.
• Supportive care is essential for patients with shock and multiple organ failure.
• Timely and appropriate antibiotic selection is critical for successful patient outcomes in severe cutaneous infections.