Chapter 134: Bacteremia and Infective Endocarditis

KEY CONCEPTS

• Bacteremia, defined as detection of bacteria in the bloodstream, is most often caused by a focal (primary) source of infection and may be complicated by the development of secondary (metastatic) foci, including infective endocarditis.

• Infective endocarditis usually occurs secondary to a bloodstream infection in adult patients with specific risk factors (eg, injection drug use, heart failure, valvular disease, and healthcare exposure) and those with implanted cardiac material (eg, prosthetic heart valves).

• A wide variety of pathogens may cause bacteremia, which is dependent on the patient population, primary source of infection, and geographic region.

• Three groups of organisms cause most cases of infective endocarditis: staphylococci, streptococci, and enterococci.

• The clinical presentation of bacteremia and infective endocarditis is highly variable and non-specific, but ranges from asymptomatic to hemodynamic instability and organ dysfunction.

• Diagnosis of bacteremia and infective endocarditis requires the integration of clinical, laboratory, and diagnostic findings.

• In patients with suspected or confirmed bacteremia, empirical antibacterial therapy should target the usual pathogens at the site(s) of suspected primary source(s) of infection and then be deescalated based on organism identification and susceptibility testing.

• Treatment of infective endocarditis involves isolation of the infecting pathogen and determination of antimicrobial susceptibilities, followed by parenteral antimicrobial therapy (in most cases) for an extended period.

• Source control which may include drainage, debridement, device removal, and definitive reconstructive manners is a critical component in managing patients with bacteremia.

• Identification and susceptibility testing of the pathogen should guide definitive therapy in patients with bacteremia or infective endocarditis, but in most cases, β-lactams, such as penicillin G (or ceftriaxone), nafcillin (or an alternative antistaphylococcal or penicillinase-resistant penicillin), and ampicillin (with or without gentamicin or ceftriaxone), remain the drugs of choice for streptococcal, staphylococcal, and enterococcal bacteremia and endocarditis, respectively.

Patient Care Process for Bacteremia and Infective Endocarditis

Collect

• Patient characteristics (eg, age, sex, height, weight, pregnancy status, allergies)

• Patient history (eg, past medical, surgical, family)

• Social history (eg, ethanol/IV drug use, recent travel, home residence, exposure to animals) and dietary habits, including intake of unpasteurized dairy products

• Current medication use, including prescription, nonprescription, and other substances, with emphasis on previous inpatient and outpatient antimicrobial use

• Objective data

  • Temperature, blood pressure, respiratory rate, complete blood count (eg, white blood cell count, red blood cell count, hemoglobin, platelets), chemistry panel (eg, serum creatinine), urinalysis

  • Results from blood and/or valve tissue cultures and specialized testing (eg, serology, polymerase chain reaction)

  • Diagnostic testing (eg, electrocardiograph, chest radiograph, echocardiography)

Assess

• Identify risk factors (eg, immunocompromised status, recent dental procedure, central venous catheter, IV drug abuse, dietary habits) (see Tables 134-1 and 134-2)

• Assess signs and symptoms (eg, temperature >100.4°F [38°C], [see Clinical Presentation box], radiographic evidence, pathogen identification, physical examination findings)

• Determine potential infectious ...