Skin and soft-tissue infections

History

When a history is being taken, it is important to elicit the following:

• Any event leading to a breach in skin integrity, which may precipitate an infection (e.g. human, insect or animal bite, ‘clenched fist’ injury, excoriation, fungal infection or puncture wound). This is important because it will help in determining the likely pathogen and choice of antibiotics as well as the need to rule out any potential foreign body that may be embedded in the wound.

• The speed with which the infection has progressed, which serves to indicate how aggressive the infection is and the urgency of needed treatment.

• Patient factors that may complicate treatment of the infection, such as

  • History of immunosuppression (e.g. diabetes, steroid use, chronic liver disease, alcoholism, malnourishment, HIV, oncology patients on chemotherapy, nephrotic syndrome).

  • Recent use of antibiotics, (i.e. failed treatment).

  • History of prosthetic heart valves, mitral valve prolapse with regurgitation, previous history of endocarditis.

  • Chronic venous stasis or lymphoedema in limbs; surgery that includes lymph node dissection or saphenous vein resection.

  • Intravenous drug use (IVDU).

• Tetanus immunization status.

• Contamination with soil or water, which would suggest unusual pathogens as the cause of the infection.

Physical examination

• Identification of signs of sepsis: haemodynamic instability, pyrexia, ‘toxic’-looking patient.

• Specific features of the infection to help narrow down the diagnosis (e.g. raised erythematous margins in erysipelas; presence of bullae and crepitus or tenderness out of proportion to physical signs, which are suggestive of necrotizing fasciitis; fetid odour, suggesting anaerobic infection; green exudates typical of Pseudomonas spp.).

• The extent of the infection (e.g. mapping areas of erythema to track progress, fluctuance that indicates a likely abscess, or lymphangitic spread).

• Location of the infection, as involvement of certain critical areas (e.g. head, face, hands, perineum) may require more intensive inpatient management and specialist consultation.

• Complicating factors that might impair successful treatment (e.g. IVDU, the presence of prosthetic heart valves).

Analgesia

Oral or parenteral analgesia should be prescribed, as most patients with SSTIs will present with pain. Simple measures—such as immobilization, elevation, heat or moist warm packs—should not be overlooked, as they may help to alleviate pain in cellulitis. Abscess pain is best resolved by timely incision and drainage.

Antibiotic therapy

Antibiotics are recommended for patients with signs of systemic toxicity, high fever, tachycardia, for those who look unwell or are immunocompromised. They are also needed for infection in high-risk areas (hands, perineal region or face) and where deep tissue infection is suspected.

It is important for the emergency physician to recognize patients with serious SSTIs and to initiate timely and appropriate care. The choice of antibiotic is often empiric and thus must be guided by the patient’s history, record of recent hospitalization and knowledge of the typical range of pathogens associated with each type of infection and their resistance patterns. The antibiotic of choice is the one that has proven efficacy against the range of expected pathogens is associated with minimal toxicity and is cost-effective. Where possible, narrow-spectrum antibiotics should be used in preference to broad-spectrum ones. Guidelines on antibiotic therapy are often deliberately non-prescriptive, reflecting the wide variety between differing patient populations, resistance patterns, risk for methicillin-resistant Staphylococcus aureus (MRSA) and local governance policies. It is also prudent to remember that SSTI clinical trials often exclude the most severely ill patients and may be powered to demonstrate non-inferiority only. The Infectious Diseases Society of America has released guidelines for treating SSTIs, including CAMRSA infections. Unlike those in inpatient or chronic care settings, emergency physicians more frequently have to initiate empiric antibiotics based on clinical judgement and prevailing anti-biograms due to the absence of culture and susceptibility results.

Current agents active against the common pathogens including MRSA and licensed for treating complicated SSTIs include linezolid, daptomycin and tigecycline. Novel approaches like phage therapy and novel antimicrobial therapy (oritavancin and tedizolid), which has equal efficacy with a better safety profile and shorter regimen, are under investigation.

Surgical intervention

Effective treatment of abscesses and carbuncles and large furuncles entails incision, drainage of pus and breaking up of loculations, followed by regular dressings. Necrotizing fasciitis requires early aggressive surgical debridement together with broad-spectrum antibiotics in order to achieve a good outcome.

Tetanus and other prophylaxis

All traumatic wounds should be considered to be tetanus-prone and treated accordingly. The patient’s immunization status should be confirmed and, where appropriate, tetanus toxoid plus tetanus immunoglobulin should be administered. Rabies prophylaxis should be considered for all feral and wild animal bites and in geographical areas where there is a high prevalence of rabies.

In cases involving human bites, consideration should also be given to screening for blood-borne pathogens such as hepatitis B virus, hepatitis C virus, HIV and Neisseria gonorrhoea .

Clinical presentation

Patients usually present with complaints of localized pain, erythema and swelling. They may be on oral antibiotics and have not responded to them. The patient may present with signs of cellulitis and regional lymphadenopathy. Frequently an indurated fluctuant swelling may be elicited, indicating the presence of an abscess. If the patient is febrile or there is systemic involvement, his or her immune status must be examined. A diligent history should be taken to assess whether a foreign body associated with an abscess may be present. Ultrasonography is extremely useful in identifying this in such cases.