Impetigo: Impetigo Contagiosa…

Impetigo Contagiosa is a very common skin infection, most frequently in children, particularly boys.  The causative bacteria are usually staphylococcal and or streptococcal organisms although mixed infections may also occur.  The most common form is characterized by discrete, thin-walled vesicles that rapidly become pustular and then rupture producing a thin, straw-colored, seropurulent discharge that exudes and dries to form loosely stratified, golden-yellow crusts.  The crusts accumulate until they are thick and friable.

The crusts can usually be removed easily, leaving a smooth, red, moist surface that collects droplets of fresh exudate…that again forms crust.  As the lesions spread peripherally at times the skin may clear centrally, as shown in some of the photographs above.  The infection can easily spread to other body parts and to other people through direct contact.

ETIOLOGY:  Most studies have shown that 50-70% of cases are caused by Staphylococcus aureus (S. aureus) with the remainder caused by S. pyogenes or a combination of these two organisms.  Streptococci may be present in developing or early impetigo, but is soon replaced with staphylococci in more mature lesions.  Group B streptococci are often associated with impetigo found in newborns.  It occurs in temperate zones, mostly during the summer…during periods of hot and humid conditions.  Common sources of infection in children include pets, dirty fingernails, and other children in grouped settings, such as day care centers, schools, and crowded housing conditions.

ACUTE GLOMERULONEPHRITIS (AGN):  Group A beta-hemolytic streptococcal skin infections have been associated with AGN.  The incidence of AGN caused by impetigo infections varies from 2% to 5% of infections in children, generally before the age of 6 years.  The prognosis is good, however…early and appropriate treatment reduces the risk and promotes a rapid recovery of AGN patients.

DIFFERENTIAL DIAGNOSIS:  Impetigo may be confused with several conditions, to include nummular eczema (click HERE),  ringworm (Tinea Corporis, click HERE), Toxicodendron dermatitis, and ecthyma.  There is a bullous form of impetigo that presents with large blisters.

TREATMENT:  A combination of systemic and tropical treatments are recommended in more severe cases.  Some authors recommend only topical treatment in mild forms while other authors discourage use of topical therapy (see references).  I usually treat with a Z pak and topical mupirocin for at least 7 days.  Alternative oral antibiotics include Rifampin, Dicloxacillin, Cephalexin, Doxycycline, Ozenoxacin, Erythromycin, Flucoxacillin and Bactrim or Septra.  I never use Bactrim or Septra due to the risk of toxic epidermal necrolysis (TEN, click HERE).  I have taken care of many patients with this debilitating and life threatening condition and believe use of sulfa drugs in this age of numerous alternatives prohibits their use…at least for me.  It is interesting that some dermatologist from other countries discourage the use of topical therapies such as mupirocin believing that use of these topicals can promote drug resistance and possible contact sensitization.  I do not agree with these concerns due for the following reasons:  1) the use of two agents, a topical along with a systemic antibiotic, decreases the risk of developing drug resistant organisms and this has been shown in numerous studies using combination versus single agent treatments for other infections, and 2) the concerns about developing contact sensitization to topical agents would proclude their use at all…the risk is very low.  To read more about Impetigo click HERE, HERE, HERE, and HERE.