Staphylococcal Infections

Key Features

• Diseases caused by staphylococci include, but are not limited to, furuncles, carbuncles, scalded skin syndrome, osteomyelitis, pyomyositis, septic arthritis, pneumonia, bacteremia, endocarditis, meningitis, and toxic shock syndrome (TSS)

• Staphylococci are the major cause of osteomyelitis and septic arthritis and are an uncommon but important cause of bacterial pneumonia

• Two toxins are recognized as playing a central role in specific diseases

  • Exfoliatin, largely responsible for scalded skin syndrome

  • Enterotoxin causes staphylococcal food poisoning

Clinical Findings

• Staphylococcal skin diseases

  • Dermal infection with S aureus causes pustules, furuncles, carbuncles, or cellulitis.

  • Skin lesions can be seen anywhere on the body but are commonly seen on the buttocks in infants and young children

  • Factors that facilitate transmission of methicillin-resistant S aureus (MRSA) or methicillin-susceptible S aureus (MSSA) include

    • Crowding

    • Compromised skin (eg, eczema)

    • Participation on contact sports teams

    • Day care attendance

    • Bare skin contact with surfaces used by others (exercise mats, sauna benches)

    • Sharing towels or other personal items

• Scalded skin syndrome

  • Skin erythema, often beginning around the mouth, is accompanied by fever and irritability

  • Involved skin becomes tender to touch

  • A day or so later, exfoliation begins, usually around the mouth

  • Inside of the mouth is red, and a peeling rash is present around the lips, often in a radial pattern

  • If erythematous but unpeeled skin is rubbed, superficial epidermal layers separate from deeper ones and slough (Nikolsky sign)

  • In the newborn, the disease is termed Ritter disease and may be fulminant

• Staphylococcal pneumonia

  • Characterized by abdominal distention, high fever, respiratory distress, and toxemia in infants

  • May occur without predisposing factors or after minor skin infections

  • Organism is necrotizing, producing bronchoalveolar destruction

  • Pneumatoceles, pyopneumothorax, and empyema are frequently encountered

  • Frequent chest radiographs to monitor the progress of disease are indicated

  • MRSA or MSSA pneumonias are rapidly progressive, severe, and often devastating

• Staphylococcal food poisoning

  • Characterized by vomiting, prostration, and diarrhea occurring 2–6 hours after ingestion of contaminated foods

• Staphylococcal endocarditis

  • Presenting symptoms are fever, weight loss, weakness, muscle pain or diffuse skeletal pain, poor feeding, pallor, and cardiac decompensation

  • Signs include splenomegaly, cardiomegaly, petechiae, hematuria, and a new or changing murmur

  • Course of S aureus endocarditis is rapid, although subacute disease occurs occasionally

• Toxic shock syndrome

  • Characterized by fever, blanching erythroderma, diarrhea, vomiting, myalgia, prostration, hypotension, and multiorgan dysfunction

  • Additional clinical features include sudden onset; conjunctival suffusion; mucosal hyperemia; desquamation of skin on the palms, soles, fingers, and toes during convalescence; DIC in severe cases; renal and hepatic functional abnormalities; and myolysis

Diagnosis

• Moderate leukocytosis (15,000–20,000/μL) with a shift to the left is occasionally found, although normal counts are common, particularly in infants

• Erythrocyte sedimentation rate is elevated

• Blood cultures are frequently positive in systemic staphylococcal disease and should always be obtained when it is suspected

• Similarly, pus from sites of infection should always be aspirated or obtained surgically, examined with Gram stain, and cultured both aerobically ...