See Midterm and Week 1 Study Guide for content covering weeks 1, 2 & 3
Common Infections
1. Impetigo
Impetigo is a superficial bacterial infection of the skin. It is classified into primary impetigo when there is a direct bacterial invasion of previously normal skin or secondary impetigo when ...
See Midterm and Week 1 Study Guide for content covering weeks 1, 2 & 3
Common Infections
1. Impetigo
Impetigo is a superficial bacterial infection of the skin. It is classified into
primary impetigo when there is a direct bacterial invasion of previously
normal skin or secondary impetigo when the infection arises at sites of minor
skin trauma. The occurrence of secondary impetigo is referred to as
impetiginization.
Impetigo is most frequently observed in children ages 2–5 years of age,
although older children of any age and adults may also be affected. The
infection usually occurs in warm, humid conditions and is easily spread
among individuals in close contact. Risk factors include poverty, crowding,
poor hygiene, and underlying scabies.
Impetigo is primarily caused by S. aureus. Group A Streptococcus (GAS)
causes a minority of cases, either alone or in combination with S. aureus.
Occasionally, MRSA is detected in some cases of impetigo.
Variants of impetigo include nonbullous impetigo, bullous impetigo, and ecthyma.
• Nonbullous impetigo—most common form of impetigo and begins as
papules that progress to vesicles surrounded by erythema. Within a
week, the papules eventually become pustules that enlarge, break
down, and form thick, adherent crusts with a characteristic golden
appearance. Lesions usually involve the face and extremities. Regional
lymphadenitis may occur, although systemic symptoms are usually
absent.
,• Bullous impetigo—Bullous impetigo is seen primarily in young children
in which the vesicles enlarge to form flaccid bullae with clear yellow
fluid, which later becomes darker and ruptures, leaving a thin brown
crust. The trunk is more frequently affected. Bullous impetigo in an
adult with appropriate demographic risk factors should prompt an
investigation for previously undiagnosed human immunodeficiency virus (HIV)
infection.
• Ecthyma—This form of impetigo, caused by group A, beta-hemolytic
Streptococcus (Streptococcus pyogenes), consists of an ulcerative form
in which the lesions extend through the epidermis and deep into the
dermis. Ecthyma resembles "punched-out" ulcers covered with yellow
crust surrounded by raised violaceous margins.
, Poststreptococcal glomerulonephritis is a serious complication of impetigo
(ecthyma). This condition develops within 1–2 weeks following infection.
Poststreptococcal glomerulonephritis manifests with edema, hypertension,
fever, and hematuria.
The diagnosis of impetigo often can be made on the basis of clinical
manifestations. A Gram stain and culture of pus or exudate is
recommended to identify whether S.
aureus and/or a beta-hemolytic Streptococcus is the cause. However,
treatment may be initiated without these studies in patients with typical
clinical presentations.
Bullous and nonbullous impetigo can be treated with either topical or oral
therapy. Topical therapy is used for patients with limited skin involvement
whereas oral therapy is recommended for patients with numerous lesions.
Unlike impetigo, ecthyma should always be treated with oral therapy.
Benefits of topical therapy include fewer side effects and lower risk for
contributing to bacterial resistance compared with oral therapy. Topical
choices to treat impetigo include the following medications for 5 days.
• Mupirocin three times daily
• Retapamulin twice daily
Extensive impetigo and ecthyma should be treated with an antibiotic
effective for both S. aureus and streptococcal infections unless cultures
reveal only streptococci. Dicloxacillin and cephalexin are appropriate
treatments. A 7-day course of oral antibiotic treatment is recommended. If
only streptococci are detected in extensive impetigo or ecthyma, oral
penicillin is the preferred therapy.
MRSA impetigo can be treated with doxycycline, clindamycin, or
trimethoprim- sulfamethoxazole (Bactrim). Crusted lesions can be washed
gently. Children can return to school 24 hours after beginning an effective
antimicrobial therapy. Draining lesions should be kept covered.
Quiz: Sally, aged 25, presents with impetigo that has been diagnosed as
infected with staphylococcus. The clinical presentation is pruritic tender,
red vesicles surrounded by erythema with a rash that is ulcerating. She
has not been adequately treated recently. Which type of impetigo is this?
a. Bullous impetigo
b. Staphylococcal scalded skin syndrome (SSSS)
c. Nonbullous
impetigo d.
Ecthyma
2. Staphylococcal Scalded Skin Syndrome
Caused by Staphylococcus aureus, it’s a variant of bullous
impetigo:Epidermal necrosis caused by bacterial exotoxins, resulting in the
epithelial layer peeling off in large, sheetlike pieces; mimics scalded-skin
, thermal burn. This serious infection is more commonly seen in children and
usually begins in the intertriginous areas.
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