Cellulitis and Erysipelas

Cellulitis

• This is infection of the dermis and subcutaneous tissue.
• The infection has poorly demarcated borders.
• It is usually caused by Streptococcus or Staphylococcus spp. but can be caused by a wide range of both aerobic and anaerobic bacteria.

Erysipelas

• This is essentially a superficial form of cellulitis, involving the dermis and upper subcutaneous tissues. The term erysipelas is not used much these days.
• It can be very difficult to distinguish cellulitis from erysipelas clinically.
• In erysipelas, borders of infection are sharply demarcated.¹
• It is caused almost exclusively by a streptococcal infection, with Lancefield group A, C or G usually implicated.²
• Appearance is that of a fiery red rash that can be painful.
• Traditionally the infection has tended to affect the face but more recently about 85% are seen on the legs.^3,4
• Erysipelas is also known as St Anthony's fire. This name comes from the Egyptian healer of the Middle Ages who was said to have been able to cure it.⁴

Cellulitis

• Cellulitis is a common problem and a common presentation in primary care.
• Cellulitis is more common and more serious in individuals with underlying diseases such as diabetes, cancer, or immunodeficiency.⁵

Erysipelas

• Erysipelas tends to occur in sporadic cases rather than outbreaks.
• The incidence declined during the 20th century, probably due to antibiotics, a less virulent streptococcus and more hygienic life styles.⁴
• It is more common among the young and the elderly with a peak incidence between 60 and 80 years.⁴

• Previous erysipelas or cellulitis
• Venous insufficiency
• Elderly
• Diabetes
• Alcoholics
• Intravenous drug use
• Immunodeficiency/immunosuppression
• Lymphoedema
• Overweight/obesity
• Athlete's foot/skin abrasions
• Inflammatory dermatoses
• Insect bites

Cellulitis

• The most common bacteria that cause cellulitis in patients with a healthy immune system are group A beta-haemolytic streptococci (Streptococcus pyogenes) and Staphylococcus aureus.⁵
• Rarely, gram-negative organisms, anaerobes, or fungi may cause cellulitis. However these organisms are more common causes in children, people with diabetes and immunocompromised individuals.¹
• Cellulitis in infants is usually caused by bloodborne spread of group B streptococci (urgent admission is required).⁵
• In children, Haemophilus influenzae was a frequent cause prior to the introduction of the HiB vaccination.
• Cellulitis occurring around surgical wounds less than 24 hours post-operatively may result from group A beta-haemolytic streptococci or Clostridium perfringens. The latter produces gas, leading to crepitus on examination.⁵
• Cellulitis is being seen with increasing frequency in HIV-infected patients.⁶

Erysipelas

• Most infections are with group A streptococci but Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae, Yersinia enterocolitica, and Moraxella spp. have been found.⁴

Cellulitis

• Cellulitis is more commonly seen in the lower limbs and usually affects one limb.⁷
• In many cases there is an obvious precipitating skin lesion, such as a traumatic wound or ulcer, or other area of damaged skin, e.g. athlete's foot.
• There is erythema, pain, swelling, and warmth of affected skin.
• Oedema and erythema often gradually blend into the surrounding skin and so the margin of the affected area may be indistinct.
• Blisters and bullae may form.
• Systemic symptoms (e.g. fever, malaise) may occur.
• Red lines streaking away from a cellulitic area represent progression of the infection into the lymphatic system. Localised adenopathy is commonly observed with lymphangitis.
• Crepitus is a sign of infection most commonly observed with anaerobic organisms.

Erysipelas

• The face or a leg are commonly affected. The arm or upper thigh are the next most common areas to be affected.⁸
• On the face, the source of the bacteria is often the nasopharynx and there may have been a recent nasopharyngeal infection.
• There may have been recent skin trauma but often no precipitating cause is noted. Athlete's foot can be the portal of entry.⁸
• Malaise, chills, and high fever (flu-like symptoms) often precede any skin lesion. Vomiting can occur.
• Within 48 hours there is a sudden and rapid onset of skin infection with pruritus, burning, and tenderness.
• The lesions begin as a small erythematous patch. This then progresses to a fiery-red, indurated, tense, and shiny plaque.⁴The margins are raised, sharply demarcated and advancing, with rapid enlargement over 3 to 6 days. There is local oedema, tenderness and warmth. The overlying skin can show streaking and there may be regional lymphadenopathy if the lymphatics are involved.⁴ The skin may then become deeper red with a bruise-like appearance and a bright red leading edge.
• Infection on the face is typically symmetrical and spreads from the paranasal area to the cheeks. Infection elsewhere tends to be unilateral.
• Fever, chills, joint pain, tiredness and loss of appetite can continue once the infection is evident.
• Severe infections may produce vesicles, bullae, petechiae and even frank necrosis.⁴
• The centre of the erythema starts to clear within 7 to 10 days and returns to normal.
• On resolution, desquamation can occur and there may be pigmentary changes that can become permanent.⁴

• Deep vein thrombosis
• Insect bite
• Superficial thrombophlebitis
• Varicose eczema
• Lymphoedema
• Chronic venous insufficiency
• Contact dermatitis
• Vasculitis
• Gout
• Septic arthritis/osteomyelitis
• Erythema nodosum
• Drug reaction
• Plant toxin allergy
• Severe ischaemia/compartment syndrome
• Necrotising fasciitis
• Metastatic carcinoma (carcinoma erysipeloides)⁷

• Usually the diagnosis is purely clinical and no investigations are required.⁹
• If there is an atypical presentation, the patient is very unwell, or there is failure to respond to treatment, cultures from possible portals of entry may be valuable. Blood culture and swabs and culture of any blister fluid may also be helpful.
• Fine needle aspiration from the leading edge of lesion may assist in diagnosis.
• X-rays, CT scan or MRI are useful if there is any concern about a foreign body in situ.
• If bullae or abscesses form, culturing the fluid from inside these lesions yields an organism in more than 90% of cases.
• Imaging should be considered if bony involvement is suspected.⁴
• If episodes are recurrent, check fasting blood glucose to exclude diabetes.

Erysipelas should be treated in the same way as cellulitis. Mild or moderate cellulitis can usually be treated in primary care. Clinical Knowledge Summary guidance regarding the management of cellulitis is as follows:⁷

• Prescribe analgesia as necessary (paracetamol or ibuprofen).
• Start flucloxacillin 500 mg four times daily (in adults) as first line in uncomplicated infection. (In sufficient doses, this covers both beta-haemolytic streptococci and penicillinase-resistant staphylococci and addition of phenoxymethylpenicillin should not be needed.^2,10)
• Erythromycin 500 mg four times daily can be used if penicillin allergic and clarithromycin (500 mg twice daily) if intolerant to erythromycin.
• Consider adding ciprofloxacin 750 mg twice daily if there has been exposure to freshwater at the site of infection. (Seek microbiology advice if contraindicated, e.g. children and growing adolescents, women who are pregnant or breastfeeding.)
• Consider adding doxycycline 100 mg once a day if there has been exposure to saltwater at the site of infection. (Seek microbiology advice if contraindicated, e.g. children under 12 years, women who are pregnant or breastfeeding.)

Other management points:

• Consider co-amoxiclav if there is facial involvement. (Seek microbiology advice if allergic to penicillin.) However, facial involvement is one of the possible criteria for hospital admission (see below).
• Rest and elevate the affected area where possible to reduce swelling and pain.
• Manage any underlying predisposing conditions, e.g. tinea pedis, skin trauma, ulcer. Clean wound site: irrigation, debride devitalised tissue.
• Advise use of an emollient to keep the skin well hydrated.
• Drawing around the margins of infection may help to identify spread/resolution.
• Assess tetanus risk and status if a puncture wound/laceration has occurred.
• Any patient with crepitus, circumferential cellulitis, or necrotic-appearing skin requires rapid surgical intervention. Necrotic skin requires examination of fascial planes to exclude necrotising fasciitis. Crepitus requires immediate debridement of tissue.
• Pain disproportionate to the physical examination or severe pain on passive movement of the extremities may indicate necrotising fasciitis and requires prompt evaluation.

Consider referral to hospital if:⁷

• Severe or rapidly worsening infection, especially if possible necrotising fasciitis
• Systemic illness or vomiting
• Evidence of complications or suspected deep infection
• Facial infection
• Suspected orbital/periorbital cellulitis
• Immunocompromised
• Diabetes (if blood sugars are unstable)
• Significant co-morbidity
• Lymphoedema is present
• Recurrent infection at the same site
• Child under 1 year
• Lack of home support/frailty/memory impairment
• Failure to respond to initial treatment with oral antibiotics

• Arrange follow-up after 7 days of treatment with antibiotics.
• Build in safety net for earlier review as needed. Advise the patient to come back sooner if antibiotics are not tolerated, skin signs worsen after 48 hours or systemic symptoms develop.
• Assess compliance with antibiotics at review.
• Consider hospital referral if no response to treatment or there is deterioration.
• Treatment with antibiotics should be for 7 days initially. 10-14 days of antibiotics may be needed to ensure complete resolution.

The most common complications include:

• Abscess formation
• Gangrene
• Thrombophlebitis/lymphangitis
• Chronic leg oedema (a late complication which may predispose to further episodes of infection)

Less common complications (occurring in <1%) include:

• Necrotising fasciitis
• Osteomyelitis
• Compartment syndrome
• Acute glomerulonephritis
• Endocarditis
• Septicaemia
• Streptococcal toxic shock syndrome

• Consensus is that any predisposing conditions should be treated to minimise risk of recurrence. However, BMJ Clinical Evidence found no RCTs or observational studies to support this.¹² Treatment of predisposing conditions may include:
  • Ensuring adequate glycaemic control
  • Weight control
  • Treatment of athlete's foot
  • For chronic leg swelling: limb elevation, calf muscle exercises and compression stockings
  • Assessment of peripheral pulses, footwear and for neuropathy in diabetics
  • Avoidance of injury to the skin as far as possible
• Prophylactic antibiotics may be considered in some people who have had episodes of recurrence at the same site. However, there is limited evidence that this will reduce future attacks and insufficient evidence about which people are more likely to benefit, or which antibiotics, doses, and durations of treatment are most likely to be effective.¹²

• Uncomplicated cellulitis or erysipelas has an excellent prognosis and most people make a complete recovery.
• Treatment without hospital admission is effective for well over 90% of patients.
• Of those who fail outpatient therapy or require admission initially, intravenous antibiotics are very effective.