The number of skin and soft tissue infections (SSTI) has skyrocketed owing to the spread of meticillin-resistant Staphylococcus aureus (MRSA). But many SSTIs — even those caused by the superbug MRSA — are minor and either heal on their own or are easily treated without antibiotics, according to updated practice guidelines for the diagnosis and management of SSTIs published by the Infectious Diseases Society of America (IDSA).

‘SSTI is a very broad category and its diagnosis and treatment can be extremely complicated, depending on many factors, from the symptoms, to the patient’s health, to the type of bacteria causing it,’ said Dennis L. Stevens, MD, PhD, lead author of the IDSA guidelines and chief of the Infectious Diseases Section of the Veterans Affairs Medical Center, Boise, Idaho.

‘We’ve provided guidance to help physicians make the correct diagnosis, establish the source and cause and determine the severity of infection, which is crucial. Antibiotics are life-saving drugs for many types of SSTIs, but should only be given when needed, and these guidelines will help physicians know when they are and are not necessary.’

SSTIs can be caused by microbes that normally are on the skin, or from other sources such as fresh or salt water or contact with another person. Bacteria can enter through open wounds or surgical incisions, animal bites, human bites or penetrating injuries to the skin. MRSA commonly is transmitted among sports teams or in gyms, in high schools and prisons; and infection can occur when the bacteria enters the skin through a cut or sore.

About half of SSTIs are caused by staph bacteria (including MRSA) and are purulent, meaning they produce boils or abscesses that contain pus, said Dr Stevens. The rest are caused by non-staph bacteria such as Group A streptococcus (GAS), which produce toxins instead of pus, and are more likely to be severe and even deadly, causing serious infections such as cellulitis, necrotising fasciitis and organgrene. These infections require speedy diagnosis, surgery to remove the infection and antibiotic treatment, the guidelines note.

Emergency room visits as a result of SSTIs nearly tripled from 1.2 million in 1995 to 3.4 million in 2005, much of the increase driven by MRSA. SSTIs account for more than 6 million visits to doctors’ offices every year, yet most pus-filled SSTIs clear on their own or should be treated with incision and draining alone, not antibiotics, Dr Stevens advised. Using antibiotics unnecessarily contributes to the development of drug-resistant superbugs.

SSTIs typically are red, swollen, hot to the touch and painful. Purulent SSTIs are usually are no larger than a few inches, have a focal point of infection and are filled with pus ‘like a miniature volcano’. Non-purulent SSTIs do not have a focal point and continue to spread. Even mild or moderate non-purulent cases typically require antibiotic treatment, sometimes provided intravenously. In the case of severe non-purulent SSTIs such as necrotising fasciitis or GAS gangrene, the infected material should be removed surgically, a treatment called debridement.

The guidelines contain a chart to help physicians quickly diagnose and treat the SSTI based on whether or not it is purulent, determining whether the infection is mild, moderate or severe, and recommending appropriate treatment. In general, doctors should be most concerned when a patient with an SSTI has a fever above 100.4, a high white blood cell count, a rapid heart rate, is breathing fast or is immunocompromised.

The updated IDSA guidelines also are the only ones that provide extensive recommendations for treating SSTIs in immunocompromised patients, including those with HIV/AIDS or who have had an organ transplant. Treating SSTIs in these patients is challenging because they likely already have been exposed to a number of antibiotics, and may be resistant to medications that typically would be prescribed, said Dr. Stevens.

The voluntary guidelines are not intended to take the place of a doctor’s judgment, but rather support the decision-making process, which must be individualised according to each patient’s circumstances.