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Chapter 9: Infections of the skin and soft tissue 399

Complications Investigations
Abscess formation, septicaemia, toxic shock-like syn- Imaging may allow detection of gas in muscle too deep
drome. for palpation (crepitus on palpation is as sensitive in
superficial muscle).
Investigations Diagnosis is confirmed by identifying clostridia in the
The diagnosis is clinical; blood cultures should be taken wound.
but are usually negative.
Management
Prevention of clostridial infections involves adequate
Management
Initial management with penicillin (Streptococcus) and wound care at the time of original trauma including ex-
flucloxacillin(Staphylococcus);erythromycinisusefulfor cision and debridement of necrotic tissue. Wounds that
patients who are penicillin allergic. If the cellulitis is ad- may be infected should not undergo primary closure. In
vanced or if it fails to respond to oral therapy, parenteral established cases penicillin is the drug of choice. Aggres-
penicillin and flucloxacillin are used, and clindamycin, sive surgical intervention with wide excision, opening of
if penicillin allergic. It is useful to outline the erythema fascial compartments, and meticulous debridement of
to allow the condition to be followed. Abscesses may re- all necrotic tissue is essential. This may require subse-
quire surgical drainage. quent reconstruction and skin grafting. The use of hy-
perbaric oxygen (HBO) to reduce anaerobic conditions
is controversial.
Clostridial myonecrosis (gas gangrene)
Definition Leprosy
Gangrenereferstodeathoftissue,andmyonecrosisrefers
specifically to muscle. Clostridial infection of wounds Definition
may result in significant infection of muscle, which de- Leprosy is a chronic indolent mycobacterial infection
velops rapidly and is potentially life-threatening. mainly of the skin.

Incidence
Aetiology/pathophysiology
The most common cause is Clostridium perfringens Rare since WHO eradication programmes.
found in soil and in the faeces of animals and humans.
Infection occurs after deep penetrating trauma. Com- Geography
promise of the blood supply as a result of the traumatic Leprosy is found primarily in Africa and Asia.
damage or as a result of longstanding vascular disease,
creates an acidic anaerobic environment and facilitates Aetiology
bacterial proliferation. It is thought that τ-toxin pro- Leprosy is caused by an intracellular acid-fast bacillus,
duced by Clostridium prevents the normal inflamma- Mycobacterium leprae.The mode of transmission is un-
tory cell infiltration and therefore allows the infection certain and the incubation may be many years.
to spread rapidly causing extensive necrosis. α-toxin has
a direct negative inotropic effect on the heart and may Clinical features
lead to shock. Fivepatternsofdiseasearerecognisedthataredependent
on the immunological response of the individual (see
Clinical features Table 9.8).
Patients develop severe pain due to myonecrosis at a site There are two immunological reactions that may oc-
of trauma with induration, blistering and oedema. In a cur in borderline or lepromatous leprosy.
limb distal pulses may be lost and crepitus is felt in the Reversal reaction (lepra type I) is seen following treat-
muscle late in the disease process. Systemic signs include ment of borderline leprosy. It is a type IV hyper-
pyrexia, tachycardia, progressing to multiorgan failure. sensitivity reaction resulting in acute inflammation