Download Cellulitis and erysipelas – spot the difference

Derm April-NH/AH
06/04/2006
16:06
Page 1
Cellulitis and erysipelas
– spot the difference
Forum
Dermatology
If cellulitis is suspected, early diagnosis and intensive treatment are
essential, writes Johnny Loughnane
Figure 1: Cellulitis due to penetrating injury–plantar surface of foot
Figure 2: Varicose ulcer with spreading cellulitis
Table 1
CELLULITIS IS A NON-CONTAGIOUS INFECTION of the skin. It is
common in general practice and a frequent cause of acute
medical admission to hospital. A spreading bacterial infection of the lower dermis and subcutaneous tissues gives rise
to tender inflammation. Erysipelas in contrast, is a more
superficial infection involving the dermis and upper subcutaneous tissues. Being more superficial, erysipelas presents
with a raised, distinct border. In contrast, the advancing
border of cellulitis tends to be rather indistinct. In practice
it is difficult to tell how deep the skin involvement is, and
therefore to differentiate between cellulitis and erysipelas.
It is probably best to consider erysipelas as a cellulitis with
superficial spread.
Streptococcus pyogens is the most frequent causative
organism. Staphylococcus aureus may also cause it. Eighty
per cent of cellulitis is due to strep. Most erysipelas is
caused by strep. Cellulitis may sometimes be caused by a
combination of staph and strep infection.
The most common site of infection is the lower limb. Bacteria gain entry via a break in the skin surface (see Table 1).
In the past, erysipelas was more common on the face but is
now more frequent on the legs.
Clinical features
Leg ulcer, diabetes, lymphoedema, obesity and peripheral
Ports of entry for bacteria
in lower limb cellulitis
• Varicose ulcers
• Trauma
• Fissuring in hyperkeratotic skin
• Tinea pedis
• Lower limb eczema
• Intravenous drug abuse
vascular disease are risk factors for developing cellulitis. In
early infection, the patient complains of pain and of feeling
generally unwell. Infection tends to progress rapidly with
development of malaise, rigors, listlessness and confusion.
Examination reveals swelling and redness that is tender and
hot to touch. The advancing edge of cellulitis is not as well
demarcated as that of erysipelas. Lymphangitis (tender, red
swelling of the lymphatics) may be present and there may
be tender regional lymphadenopathy. The diagnosis is essentially clinical. Because of the importance of early diagnosis
and treatment, always closely inspect and feel the lower
limbs of patients at risk, looking for the signs of inflammation outlined above.
FORUM April 2006 61
Derm April-NH/AH
06/04/2006
16:06
Page 2
Forum
Dermatology
Table 2
Table 3
Indications for admission
Initial antibiotic treatment
• Severe or rapidly worsening infection
• Flucloxacillin 1g QID
• Patient systemically unwell or vomiting
• Flucloxacillin 1g QID + amoxicillin 1g TID
• Uncertainty regarding the diagnosis (need to outrule
DVT)
• Flucloxacillin 1g QID + phenoxymethylpenicillin 500mg
QID
• Orbital or periorbital cellulitis
• Phenoxymethylpenicillin 1g QID, if erysipelas
• Evidence of complications
• Erythromycin 500mg-1gm QID if penicillin allergy
• Immunocompromised patient
• Diabetes mellitus – if unstable
• Significant comorbidity (eg. heart failure, malignancy,
respiratory failure, renal failure)
• Children under one year of age
• Frail elderly without good home support
• Lack of response to home treatment at 48 hours
Complications
Septicaemia may complicate cellulitis, and a mortality
rate of 5% has been reported in patients requiring hospital
admission for cellulitis. Strep nephritis is rare. Cellulitis
damages the lymphatic drainage system which may be subclinical or may cause symptomatic lymphoedema. It is
estimated that up to 7% of people will develop chronic
oedema after an episode of leg cellulitis. Once established,
lymphoedema predisposes to further episodes of cellulitis.
Twenty-five per cent of patients admitted to hospital with
cellulitis will suffer recurrence in the future.
Treatment
A high index of suspicion, leading to prompt diagnosis and
treatment, is vital. Appropriate antibiotics at adequate
dosage and for a sufficient length of time should be given
systemically. Patients who are not systemically unwell and
do not have significant co-morbidities can be managed at
home. Many will need admission to hospital for treatment
(see Table 2).
The patient should rest and elevate the affected limb. This
reduces swelling and pain. Paracetamol 1g QID may be
needed for pain. It is best to avoid NSAID use as there have
been reports linking their use with the development or
aggravation of necrotising fasciitis. We have little evidence
to guide our choice of antibiotic in the treatment of cellulitis so treatment must be empirical. The chosen antibiotic
should cover staph and strep infection.
High dose flucloxacillin will cover both streptococci and
penicillinase-resistant staphylococci. Flucloxacillin 1g QID,
used alone, is recommended as initial treatment.
Some recommend combining this with amoxycillin 1gm
TID or phenoxymethylpenicillin 500mg QID. However, penetration of phenoxymethylpenicillin in tissue is poor.
In patients allergic to penicillin use erythromycin 500mg1000mg QID. Remember that 20% of staph and strep are
resistant to erythromycin. Therefore, if erythromycin is used,
early follow-up is essential to ensure response. Clindamycin
is an alternative for penicillin-allergic patients.
As erysipelas is almost always due to strep infection, highdose phenoxymethylpenicillin (1g QID) used alone is
advocated by some as a suitable initial treatment. Antibiotics
should be continued for at least 10 days. Patients should
then be reviewed and treatment continued if signs of infection persist. Be prepared to continue antibiotics for up to four
weeks. Use potassium permanganate soaks (for 20 minutes)
if there is any exuding area, eg. infected varicose ulcer. The
patient should be followed up after 48 hours and advised to
call earlier if there is any significant deterioration.
Follow up
As stated, there is a significant risk of recurrence. To
reduce this risk:
Treat underlying cause
• Tinea pedis – antifungal therapy
• Venous ulcer – compression bandaging, varicose vein
surgery
• Diabetes mellitus – optimise control
• Leg oedema – support stockings, diuretic.
• Trauma – advise on injury avoidance.
Prophylactic antibiotics
• Phenoxymethylpenicillin 500mg BD for one month,
followed by 500mg daily
• Erythromycin 500mg daily if allergic to penicillin
• Prophylactic antibiotics should be considered for patients
with high risk factors who have had two episodes of cellulitis.
Cellulitis is a common problem in primary care. A high
index of suspicion needs to be maintained to facilitate early
diagnosis and intensive treatment. Consider admission in
severe disease or if there is significant co-morbidity. Early
follow-up should be arranged to check response to treatment.
Johnny Loughnane is in practice in Co Limerick
www.icgp.ie
62 FORUM April 2006