Staphylococcal Infections

James K. Todd

doi:10.1542/pir.26-12-444

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James K. Todd, MD*

^*Professor of Pediatrics, Microbiology, and Preventive Medicine/Biometrics, University of Colorado School of Medicine; Director of Epidemiology and Clinical Microbiology, The Children’s Hospital, Denver, Colo

Objectives

After completing this article, readers should be able to:

Describe the major clinical syndromes of Staphylococcus aureus infection.
Know the key laboratory tests for S aureus.
Discuss the treatment of S aureusinfection.
Recognize the key components of therapy for toxic shock syndrome.

Definitions

Staphylococci are hardy aerobic bacteria that are present in the environment and as normal flora of humans and animals. They are resistant to heat and drying and may be recovered from the environment months after contamination. These organisms are gram-positive cocci that grow in characteristic grapelike clusters. Staphylococci are distinguished from streptococci by a positive catalase (H₂O₂) test. Species are classified as Staphylococcus aureus if they are coagulase-positive or as one of many species of coagulase-negative staphylococci (eg, S epidermidis, S saprophyticus). S aureus is the most common cause of pyogenic infection of the skin; it also may cause osteomyelitis, septic arthritis, wound infection, abscess, pneumonia, empyema, endocarditis, pericarditis, meningitis, and toxin-mediated diseases, including food poisoning, staphylococcal scarlet fever, scalded skin syndrome, and toxic shock syndrome (TSS). Coagulase-negative staphylococci tend to be less pathogenic unless a foreign body (eg, intravascular catheter) is present.

Epidemiology

Many neonates are colonized with S aureus within the first postnatal week. Thereafter, up to 50% of healthy individuals carry at least one strain of S aureus in the anterior nares at any given time. The organisms may be transmitted from the nose to the skin, where colonization seems to be more transient. Persistent umbilical perianal and vaginal carriage has been described. S aureus generally is transmitted by direct contact, primarily on the hands. Autoinfection is common. Handwashing by caretakers between contacts with patients decreases the spread of staphylococci from patient to patient. Many different strains of S aureus are capable of causing a wide variety of diseases (Fig. 1); these …