Infectious cellulitis is a common bacterial skin infection of the lower dermis and subcutaneous tissue. It results in a localized area of red, painful, swollen skin and systemic symptoms. If left untreated, infectious cellulitis can be fatal.
Similar symptoms are experienced with the more superficial infection, erysipelas, so infectious cellulitis and erysipelas are often considered together.
WHO SUFFERS FROM INFECTIOUS CELLULITIS?
Infectious cellulitis affects people of all ages and races. Risk factors for infectious cellulitis are:
- Previous episodes of infectious cellulitis
- Cracking of the toes or heels, for example, due to athlete's foot, tinea pedis, or cracked heels
- Venous disease, e.g. e.g. gravitational eczema, leg ulceration, and/or lymphedema
- Current or previous injury, for example, trauma, surgical wounds, radiation therapy
- Immunodeficiency, for example, human immunodeficiency virus (HIV) infection
- Immunosuppressive drugs
- chronic kidney disease
- Chronic liver disease
WHAT CAUSES INFECTIOUS CELLULITIS?
The most common bacteria that cause infectious cellulitis are Streptococcus pyogenes (two-thirds of cases) and Staphylococcus aureus (one-third). The rarest causes of infectious cellulitis are:
- Pseudomonas aeruginosa, usually in a puncture wound of the foot or hand
- Haemophilus influenza, in children with facial infectious cellulitis.
- Anaerobes, Eikenella, Streptococcus viridans, by human bite
- Pasteurella multocida, from a cat or dog bite.
- Vibrio vulnificus, due to exposure to saltwater, for example, a coral injury
- Aeromonas hydrophila, by exposure to fresh or saltwater, for example, following leech bites.
- Erysipelothrix(erysipeloid), in butchers.
- Other forms of skin injury that can increase bacterial exposure and infectious cellulitis infection are surgical wounds and insect bites.
- Infectious cellulitis is not usually contagious, since it affects the deeper layers of the skin.
WHAT ARE THE CLINICAL FEATURES OF INFECTIOUS CELLULITIS?
- Infectious cellulitis can affect any area, but most often it affects the extremities
- It is usually one-sided; a bilateral disease is more often due to another condition.
- It can appear on its own or complicate an underlying skin condition or wound.
- The first sign of the disease is usually a feeling of being unwell, with fever, chills, and tremors (rigors). This is due to the presence of bacteria in the bloodstream (bacteremia). Systemic symptoms are soon followed by the appearance of a localized area of painful, red, swollen skin.
OTHER SIGNS ARE
- dimpled skin (peau d'orange)
- Erosions and ulceration
- abscess formation
- Purpura: petechiae, ecchymoses, or hemorrhagic bullae
Infectious cellulitis may be associated with lymphangitis and lymphadenitis, which are due to bacteria within the lymphatic vessels and local lymph nodes. A red line runs from the site of infection to nearby, tender, swollen lymph nodes.
After successful treatment, the skin may flake or peel off while it heals. This can cause itching.
WHAT ARE THE COMPLICATIONS OF INFECTIOUS CELLULITIS?
Severe or rapidly progressive infectious cellulitis can lead to complications that require prompt treatment:
- Necrotizing fasciitis(a more serious soft tissue infection recognized by severe pain, pale skin, numbness, purpura, ulceration, and necrosis)
- gas gangrene
- Severe sepsis(blood poisoning)
- Infection of other organs, eg pneumonia, osteomyelitis, meningitis
- Endocarditis(infection of the heart valves) or
Sepsis is recognized by fever, malaise, loss of appetite, nausea, lethargy, headache, and muscle and joint pain. Severe infection causes hypotension (low blood pressure, collapse), reduced capillary circulation, heart failure, diarrhea, gastrointestinal bleeding, kidney failure, and loss of consciousness.
HOW IS INFECTIOUS CELLULITIS DIAGNOSED?
The diagnosis of infectious cellulitis is based primarily on clinical features, including a physical examination. Investigations may reveal:
- Leukocytosis (increased white blood cell count).
- Elevation of C-reactive protein (CRP)
- The causative organism, in the culture of blood or pustules, scabs, erosions, or wound.
- Diagnostic imaging can be done. For example:
- Chest x-ray in case of heart failure or pneumonia
- Doppler ultrasound to look for blood clots (deep vein thrombosis)
- MRI in case of necrotizing fasciitis.
WHAT IS THE DIFFERENTIAL DIAGNOSIS OF INFECTIOUS CELLULITIS?
Infectious cellulitis is often diagnosed when another inflammatory skin disease is actually responsible for the redness and swelling. Conditions that cause "infectious pseudo cellulitis" include:
- Eczema/stasis dermatitis, contact factors
- Fungal infection, eg tinea corporis, tinea pedis
- Deep venous thrombosis
- drug rash
- Insect bites and stings
- Radiation damage after radiotherapy
- Inflammatory breast cancer (erysipeloid carcinoma).
WHAT IS THE TREATMENT OF INFECTIOUS CELLULITIS?
Infectious cellulitis is potentially serious. The patient should rest and elevate the affected limb. The edge of the inflamed area should be marked to monitor the progression/regression of the infection.
Knowledge of local organisms and resistance patterns is essential to select the appropriate antibiotics. The treatment of infectious cellulitis is becoming more complicated due to the increasing rates of methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pyogenes resistant to macrolides or erythromycin.
TREATMENT OF UNCOMPLICATED INFECTIOUS CELLULITIS
If there are no signs of systemic disease or extensive infection, patients with mild infectious cellulitis can be treated with oral antibiotics at home, for a minimum of 5-10 days, but they must avoid the spread of bacteria and did you know that there are six bacteria that coexist on the screen of your smartphone? In some cases, antibiotics are continued until all signs of infection (redness, pain, and swelling) are gone, sometimes for several months. Treatment should also include
- Analgesia to reduce pain
- Adequate water/fluid intake
- Treatment of coexisting skin diseases, such as venous eczema or tinea pedis