Cellulitis Flashcards
What is cellulitis?
This is infection of the dermis and subcutaneous tissue.
The infection has poorly demarcated borders.
What is erysipelas?
This is essentially a superficial form of cellulitis, involving the dermis and upper subcutaneous tissues.
It can be very difficult to distinguish cellulitis from erysipelas clinically.
In erysipelas, borders of infection are sharply demarcated.
Appearance is that of a fiery red rash that can be painful.
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.
What is the most common causative organisms for cellulitis and erysipelas?
Cellulitis and erysipelas are commonly seen as manifestations of the same condition and the terms are often used interchangeably.
They are acute, painful and potentially serious infection of the skin and subcutaneous tissues.
The most common causative organisms are Streptococcus or Staphylococcus spp. but they can be caused by a wide range of both aerobic and anaerobic bacteria.
What are the risk factors for cellulitis and erysipelas?
They are more common and more serious in individuals with underlying diseases such as diabetes, cancer or immunodeficiency.
Other risk factors include: o Previous erysipelas or cellulitis. o Venous insufficiency. o Elderly age. o Alcohol dependency o IV drug misuse o Lymphoedema. o Overweight/ obesity o Athlete’s foot/skin abrasions. o Inflammatory dermatoses. o Insect bites. o Pregnancy.
What is the causative organisms of cellulitis around surgical wounds?
Cellulitis occurring around surgical wounds less than 24 hours postoperatively may result from group A beta-haemolytic streptococci or Clostridium perfringens.
The latter produces gas, leading to crepitus on examination.
What are the causative organisms of erysipelas?
Most infections are with group A streptococci but Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae type b, Yersinia enterocolitica and Moraxella spp. have been found.
What are the rare causative organisms of cellulitis and erysipelas?
More rarely, cellulitis or erysipelas may be caused by other organisms:
H. influenzae type b - in children less than 6 years of age.
Pasteurella multocida, Streptococcus anginosus (formerly known as Streptococcus milleri), and Capnocytophaga canimorsus - following cat or dog bites.
Vibrio vulnificus, Aeromonas hydrophila - following sea or fresh-water exposure.
Erysipelothrix rhusiopathiae - in butchers, vets or fish handlers.
Mycobacterium marinum - in aquarium keepers.
What is the presentation of cellulitis?
Cellulitis is more commonly seen in the lower limbs and usually affects one limb.
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 cellulitis 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.
Why is cellulitis in the hand concerning?
Cellulitis in the hands is particularly concerning because due to the small spaces, swelling can cause compression quickly in the hand and especially fingers.
This can lead to nerve and blood supply damage. Therefore, it is important to assess sensation and capillary refill. If there is any concern regarding the neurovascular integrity of an infected hand this is an orthopaedic emergency and the patient should be admitted for iv antibiotics and debridement.
Why are dog, cat and human bites treated differently?
Dog, cat and human bites need to be treated slightly differently because infection is usually polymicrobial.
Mouths are full of a variety of bacteria and a bite usually inoculates more than one of these. (TCD)- Co-amoxiclav is the first line antibiotic for mammal bites.
How does erysipelas in the leg present?
There may have been recent skin trauma but often no precipitating cause is noted. Athlete’s foot can be the portal of entry.
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. The 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. The skin may then become deeper red with a bruise-like appearance and a bright red leading edge.
Severe infections may produce vesicles, bullae, petechiae and even frank necrosis.
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.
How does erysipelas on the face present?
On the face, the source of bacteria is often the nasopharynx and there may have been a recent nasopharyngeal infection.
Infection on the face is typically symmetrical and spreads from the paranasal area to the cheeks. Infection elsewhere tends to be unilateral.
What are the differentials for cellulitis and erysipelas?
DVT Insect bite Superficial thromobophlebitis Varicose eczema Pyoderma granulosum Chronic venous insufficiency Contact dermatitis Vasculitis Gout Septic arthritis/ osteomyelitis Erythema nodosum Drug reaction Severe ischaemia/ compartment syndrome Necrotising fasciitis Metastatic carcinoma (carcinoma erysipeloides)
Investigations for cellulitis and erysipelas
Usually the diagnosis is purely clinical, and no investigations are required.
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, usually in those patients where the diagnosis of cellulitis is in doubt.
There is often a raised CRP level, but a normal CRP level does not rule out an infection.
Fine-needle aspiration from the leading edge of the 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.
If the lesion is purulent, it should be debrided and cultured.
Imaging should be considered if bone involvement is suspected.
If episodes are recurrent, diabetes and immunodeficiency should be excluded.
Management of cellulitis and erysipelas
Erysipelas should be treated in the same way as cellulitis. Mild or moderate cellulitis can usually be treated in primary care. General measures include rest, elevation of any affected limbs, and analgesia. Analgesia should be considered as necessary (paracetamol or ibuprofen).
Flucloxacillin 500 mg four times daily (in adults) is usually given as first line in uncomplicated infection. In sufficient doses, this covers both beta-haemolytic streptococci and penicillinase-resistant staphylococci.
Oral antimicrobials are as effective as parenteral antimicrobials for the treatment of uncomplicated cellulitis[5].
Erythromycin 500 mg four times daily, clarithromycin (500 mg twice daily) or doxycycline 200 mg on the first day and then 100 mg daily for 5-7 days can be used if the patient is penicillin allergic.
Alternative first-line antibiotic if the infection is near the eyes or nose is co-amoxiclav 500/125 mg three times a day orally for 7 days. If the person is allergic to penicillin they can have clarithromycin 500 mg twice a day for 7 days with metronidazole 400 mg three times a day for 7 days.
Alternatives for severe infection include co-amoxiclav, clindamycin orally or cefuroxime or ceftriaxone intravenously.
Manage any underlying predisposing conditions - eg, tinea pedis, skin trauma, ulcer. Clean the wound site: irrigate; debride devitalised tissue.
Advise use of an emollient to keep the skin well hydrated.
Drawing around the margins of infection may help to identify the spread/resolution.
Assess tetanus risk and status if a puncture wound/laceration has occurred.
When is necrotising fasciitis suspected?
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.
