AntiInfectiveMeds

Urinary tract infections, including uncomplicated cystitis, pyelonephritis, prostatitis, and perinephric abscess, are the most common type of clinical infections produced by enterococci (Box 1). Most enterococcal urinary tract infections are nosocomial and are associated with urinary catheterization or instrumentation. Nosocomial enterococcal bacteremias are commonly polymicrobial. Portals of entry for enterococcal bacteremia include the urinary tract, intra-abdominal or pelvic sources, wounds (especially burns, decubitus ulcers, and diabetic foot infections), intravascular catheters, and the biliary tree.

Streptococcus pyogenes is a human pathogen without an animal reservoir. Group A streptococci (GAS) cause most streptococcal disease, but other groups are important pathogens in some settings (Box 1). Group A streptococcal infections have the highest incidence in children younger than age 10. The asymptomatic prevalence is also higher (15-20%) in children, compared with that in adults (<5%).

In the late 1980s, invasive GAS infections occurred in North America and Europe in previously healthy individuals of all ages. This illness is associated with bacteremia, deep soft-tissue infection, shock, multi-organ failure, and death in 30% of cases. StrepTSS occurs sporadically, although minor epidemics have been reported. Most patients present with a viral-like prodrome, history of minor trauma, recent surgery, or varicella infection.

S pneumoniae may exist in humans as either a nasopharyngeal colonist or as a pathogen in one of many clinical syndromes (Box 1). Although S pneumoniae has been found in other mammals, humans are thought to be the principal reservoir. As a colonist, S pneumoniae is found in up to 40% of children and 10% of adults.

This section focuses on the clinical findings, diagnosis, and treatment of pneumococcal meningitis. Please also see site for a general discussion of meningitis.

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.