Treatment for impetigo

Impetigo is a bacterial skin infection, the fourth most common dermatological skin disorder in children seen in general practice. Most patients are treated by general practitioners. Proper hygiene and adequate treatment supposedly control the infection, but over the past decade the incidence of impetigo has not declined in the Netherlands.¹ For the individual patient, impetigo is a minor disease as a cure can be expected within weeks with most treatments. In developed countries, serious complications such as acute glomerulonephritis are rare.² Nevertheless the impact of an impetigo outbreak can be considerable. The unattractive appearance of the lesions may worry parents, and children are often barred from schools and kindergartens because of fear of spread of the infection. Outbreaks of impetigo caused by multiple resistant staphylococci have been reported.³,⁴ For the clinician the choice of treatment will be based primarily on effectiveness and side effects and then on costs and convenience for the patient. A responsible doctor will also consider the problem of increasing bacterial resistance.

Although many authors say that the natural course of impetigo is favourable and spontaneous resolution may be expected within weeks, research confirming this is scarce. Evidence from the placebo arms of controlled trials shows a considerable variance in cure rates after one week of treatment, up to 42%.²

One of the conclusions of our recent Cochrane review is that treatment with topical antibiotics with either mupirocin or fusidic acid is at least as or more effective than treatment with oral antibiotics.² These results apply to localised impetigo, because trials that study the effect of a topical treatment usually exclude patients with extensive forms. Topical antibiotics other than mupirocin and fusidic acid can be considered inferior. Among the numerous β-lactamase resistant oral antibiotics studied in trials, none has been proved superior. Many of these studies were underpowered and designed to study a given treatment for several skin infections combined rather than to study impetigo. Oral penicillin was found to be inferior to most other orally administered antibiotics. Side effects (especially gastrointestinal) of topical antibiotics are generally less than with oral antibiotics.

We have no evidence to support the therapeutic value of disinfecting agents such as chlorhexidine or povidone-iodine. These treatments have hardly been studied. Studies establishing the value of disinfecting agents are therefore most welcome. Other questions that need to be answered are whether prompt treatment of impetigo reduces contagiousness or prevents epidemics, and whether barring affected children from school is an effective measure towards prevention.

According to the evidence the best choice for treatment of limited impetigo is either topical mupirocin or topical fusidic acid. Recently, however, concern has been raised about the use of topical fusidic acid. Therising resistance rates of Staphylococcus aureus against fusidic acid call for its prudent use.³,⁵,⁶

Although a link between prescribing antibiotics and resistance has been established at the level of the individual,⁷ this relation is unclear at practice level or even group level.⁸ Generally, higher prescription rates seem to be associated with higher resistance rates. Moreover, prolonged use of an antibiotic in chronic conditions seems to be an important factor in the promotion of resistance.⁹,¹⁰ This means that a short antibiotic course of one to two weeks for acute primary impetigo should be relatively harmless, but impetiginised eczema or atopic dermatitis should not be treated with topical antibiotics.

The effectiveness of any antibiotic is dependent on the susceptibility of the causative bacteria. In impetigo this is usually S aureus. Resistance rates in staphylococci against fusidic acid vary considerably between regions and in time.⁶,¹⁰ Therefore, treatment of impetigo should be guided by susceptibility testing of a S aureus isolate obtained from the patient. However, this time consuming procedure is hardly feasible in general practice and therefore is seldom done.

The final choice of treatment can be determined best by regional or national guideline developing bodies. Knowledge of local resistance patterns on the basis of surveillance of specimens derived from general practice should be incorporated in these documents. Furthermore, they may contain policies to reserve certain antibiotics for the treatment of other, more serious infections. For example, systemic fusidic acid is considered vital in the treatment of severe bone infections, and mupirocin is a cornerstone in eradication of methicillin resistant S aureus carriage. Frequently updated guidelines of this kind are not available yet in most parts of the world.