(1997; 132 pages) [French] [Spanish]
Staphylococcal and streptococcal infections
Staphylococcal and streptococcal infections of the skin are very common where the climate is hot and humid, where standards of hygiene are compromised, and among immunodeficient patients. While lesions often develop on previously healthy skin, pre-existing eczematous lesions and other dermatoses such as insect bites and scabies lesions can also become infected.
Impetigo is a highly contagious superficial pyoderma caused by staphylococci, streptococci, or a combination of both organisms. It is particularly common in infants and small children, but rare in adults. It is characterized by the formation of vesicular lesions, which become pustular and rupture, leaving crusted lesions. These lesions heal without scarring. The bullae may be localized or disseminated. Pruritus is common and the infected area is often extended by scratching. A severe and potentially fatal variant of the disease, Staphylococcal scalded skin syndrome, occurs in infants, which is characterized by the development of a generalized bullous eruption. When these lesions rupture, the entire skin has a scalded appearance. Epidermal splitting occurs in the granular layer of the epidermis and therefore the systemic impact of dehydration and/or imbalance of electrolytes is usually not severe. In older children who have already been exposed to staphylococci, a scarlatiniform rash is more common. Glomerulonephritis may occur as a complication of severe impetigo caused by Streptococcus pyogenes.
Poor sanitation is partially responsible for the high incidence of impetigo in developing countries. Endemic scabies is another cause. The lack of adequate medication to treat the minor cuts and abrasions to which many children are continuously exposed is also an important factor in the high rate of infection.
Both mothers and teachers should be aware that cuts and abrasions provide an entry point for the bacteria that cause impetigo.
Ecthyma is a variant of impetigo. The lesions, which extend deeper into the dermis, heal with scarring. The lesions often occur on the legs of children and infection is usually secondary to insect bites.
Cellulitis and erysipelas are streptococcal infections of the subcutaneous tissues, which usually result from contamination of minor wounds. Both conditions are characterized by acute localized inflammation and oedema. The lesions are more superficial in erysipelas than in cellulitis and have a well-defined, raised margin. Potentially fatal systemic toxaemia may supervene in patients who remain untreated. Recurrent cellulitis or erysipelas may result in chronic lymphoedema which may, in turn, serve as a predisposing factor for recurrent infection. In young children, facial lesions similar to those of cellulitis and erysipelas may be caused by Haemophilus influenzae.
Folliculitis and furunculosis, which result from infection of hair follicles, are usually caused by staphylococci. When they occur in patients who are either diabetic or immunocompromised, they require particularly careful management. In these circumstances, carbuncles (clusters of furuncles) with multiple openings sometimes form as a result of invasion and necrosis of the dermis.
Impetigo may be prevented by washing minor skin abrasions with soap and water and applying a topical antiseptic. These materials should therefore be made available at the community level. Mild localized superficial infections can often be treated effectively with topical antiseptics such as gentian violet, brilliant green, chlorhexidine, polyvidone iodine or thiomersal. The skin should be kept clean by washing frequently and drying after washing. Superficial crusts should be gently separated with soap and water or a weak antiseptic solution such as aluminium diacetate, 0.65% solution, or potassium permanganate, 0.01% solution.
Mupirocin, 2% cream, is of value, particularly in the treatment of impetigo, but it is expensive. Preparations containing neomycin and bacitracin are also effective, but there is a slight risk of sensitization, especially to neomycin, with continued or repeated use. Clioquinol, 1-3% ointment, applied three times daily, is an alternative that is both effective and inexpensive. Topical use of preparations containing antimicrobials widely used in general medicine, including penicillins, sulfonamides, streptomycin and gentamicin, should be avoided. Because of the possibility of inducing contact dermatitis and favouring the emergence of resistant organisms, these antibiotics should be reserved for the systemic treatment of severe infections.
Widespread superficial and deep-seated infections associated with fever or infections in immunocompromised individuals require treatment with a systemic antibiotic. Baths are also important. Topical application of potassium permanganate (1:10000) or copper sulfate (1:1000) solution, followed by debridement and removal of crusts, is of value. Whenever possible, antimicrobial therapy should be based on the results of in vitro sensitivity tests. Systemic administration of penicillins, or erythromycin or a tetracycline in penicillin-sensitive individuals, is effective in streptococcal infections. Procaine benzylpenicillin, 600000 IU i.m. daily (25000-50000 IU/kg i.m. daily in children under 12 years) for at least 10 days, is necessary in severe cases to try to prevent glomerulonephritis. However, cloxacillin holds advantage in the management of some staphylococcal infections, particularly when the sensitivity of the organism is unknown and where penicillin-resistant organisms are prevalent. In infants, the need for parenteral fluids must be evaluated. Newborn babies or infants in nurseries should be isolated to avoid transmission of the disease in susceptible individuals.