This section focuses on the clinical findings, diagnosis, and treatment of pneumococcal pneumonia. Bacteremia, progressive respiratory failure, and hemodynamic instability (ie, septic shock) are the most severe complications of pneumococcal pneumonia. As noted above, patients with either anatomic or functional asplenia are at particularly high risk for sepsis. Spread of infection via either contiguous extension or hematogenous routes constitutes the basis of extrapulmonary complications.
Staphylococcus aureus colonizes the human skin, vagina, nasopharynx, and gastrointestinal tract. Colonization occurs shortly after birth and may be either transient or persistent. Published studies differ widely in estimates of the prevalence of S aureus carriage.
Osteomyelitis is divided into two subcategories based on the acuity of onset. Acute osteomyelitis, more commonly seen in children, is associated with sudden onset of bony pain, fever, and malaise. Acute disease is often the result of seeding of the bone during S aureus bacteremia, with the most common anatomic locations corresponding to highly vascularized osseous areas such as the metaphyses of long bones. Chronic osteomyelitis is a more indolent process, characterized by low-grade fevers and chronic nonhealing ulcers or draining sinus tracts in the skin overlying the infected bone.
Staphylococci (both S aureus and CoNS) have emerged as the two most common organisms cultured from patients with primary bloodstream infections. The term “primary bacteremia” refers to positive blood cultures without an identifiable anatomic focus of infection. Differentiation of primary bacteremia from infective endocarditis (IE), in which infection of the cardiac valves leads to continuous bacterial seeding of the bloodstream, may challenge even the most experienced clinician. Primary S aureus bacteremia is associated with insulin-dependent diabetes, the presence of a vascular graft, and, most significantly, the presence of an indwelling intravascular catheter.
The toxic shock syndrome (TSS) is a heterogeneous complex of symptoms attributed to TSST-1 toxin-producing S aureus. Two variants have been described: menstruation-associated and nonmenstrual disease. Cases of menstruation-associated disease are correlated with the use of superabsorbent tampons.
Impetigo and staphylococcal scalded skin syndrome (SSSS) are primarily childhood diseases. More than 70% of cases of impetigo are caused by S aureus, with the remainder attributed to pyogenic streptococci or mixed infection. Impetigo begins as a scarlatiniform eruption in a previously traumatized area that blisters then ruptures to form a wet, honey-colored crust. Common sites for infection are the face and trunk.
S aureus is the leading bacterial cause of pyogenic skin lesions (Box 46-1). Folliculitis, infection of the hair follicles, is a local suppurative process causing indurated papules or pustules, often with a hair exiting from the center of the lesion. There is local erythema and tenderness, but the patient is not systemically ill.
Papillomaviruses (HPVs) cause skin warts, most commonly in children and young adults, which may reflect acquired immunity in older age groups (Box 1). Laryngeal papillomas are found most commonly in young children and middle-aged adults. Genital warts (condylomas) are most common among sexually active patients and are sexually transmitted. Recent studies suggest that genital HPV infections may occur in 20% of females and are associated with cervical dysplasia, neoplasia, or both.
This SITE includes a variety of viral infections that produce severe systemic syndromes (Table 1). In some cases, these infections are transmitted by arthropod vectors; in others, they are acquired by direct contact with the reservoir animal or its excreta.
Colorado tick fever, an acute disease characterized by fever, headache, and severe myalgia, was originally described in the nineteenth century and is now believed to be one of the most common tick-borne viral diseases in the United States. Although hundreds of infections occur annually, the exact number is not known because it is not a reportable disease.