Causative Organisms and Clinical Presentation of Facial Cellulitis

Primary Causative Organisms

Other β-hemolytic streptococci, including groups B, C, and G, can cause facial infections, in addition to group A Streptococcus, which is the leading pathogen 1
Streptococci typically cause diffuse, rapidly spreading infection with sharply demarcated borders and raised edges, with most facial infections attributed to group A Streptococcus specifically 2
S. aureus rarely causes facial cellulitis unless associated with penetrating trauma, injection sites, or underlying abscesses, with both methicillin-sensitive S. aureus (MSSA) and community-acquired methicillin-resistant S. aureus (CA-MRSA) being potential causative agents 1, 3
Staphylococcal cellulitis is typically more localized compared to streptococcal infections 2

Small, clinically inapparent breaks in the skin are often the portal of entry for facial cellulitis, with direct trauma to the facial skin being a common precipitating factor 1, 3
Preexisting skin infections such as impetigo or ecthyma can serve as the source of facial cellulitis, with insect bites or other breaks in the skin barrier facilitating bacterial entry 1, 3
Extension from adjacent sinusitis, particularly ethmoid sinusitis, can cause facial cellulitis, with fissured or macerated interdigital toe spaces potentially harboring streptococci in lower extremity cellulitis 1, 3
Cat or dog bites can introduce Pasteurella species or Capnocytophaga canimorsus as causative pathogens in facial cellulitis 1

Facial cellulitis caused by streptococci presents with rapid spread, fiery red, tender, painful appearance 1, 4
Blood cultures are positive in only 5% of facial cellulitis cases, with needle aspiration yielding organisms in only 5-40% of cases, and punch biopsy cultures being positive in 20-30% of cases 1
The American College of Emergency Physicians and the Infectious Diseases Society of America recommend considering the diagnosis of facial cellulitis in patients with symptoms of infection, including fever, chills, or rigors, and signs of localized infection, such as erythema, swelling, and warmth 1, 3