Bacteremia

Background

Bacteremia is presence of bacteria in the blood, which is typically a sterile environment. This is distinct from sepsis, which is the body's response to the infection.

• Primary bacteremia is the result of direct inoculation of bacteria into the bloodstream. Most commonly the result of IV drug use or contaminated venous catheters
• Secondary bacteremia occurs when bacteria enters via an alternate site such as cuts in the skin, mucous membranes, or genitals

Risk Factors

• Diabetes
• HIV infection
• Hemodialysis
• Immunosupression
• Glucocorticoid therapy
• IV drug use

Common Pathogens

• Staph aureus is one of the most common cause of bacteremia in healthcare setting
• Gram negative bacteremia accounts for a quarter to half of bloodstream infections.
  • The most common isolated pathogens include E. coli, K. pneumonia, P. Aeruginosa, Proteus spp.
• Group A strep accounts for 0.6% of bacteremia.

Clinical Features

A host response may result in sepsis

• Typically present with fever, chills and hypotension.
• The presence of chills is also independently associated with blood stream infections

Alternatively bacteria may spread hematomagously to distant sites in body:

• Endocarditis
• Meningitis
• Osteomyelitis

Evaluation

Source

• In gram positive bacteremia, more notably Staph aureus, consider sources from skin ulcerations, respiratory tract infections, IV drug use, and indwelling catheters
• In gram negative bacteremia, common sources include respiratory tract and central venous catheters. In the elderly, consider urinary tract infections.

Blood Cultures

• Obtain blood cultures prior to antibiotic therapy. Indicated for suspected bacterial infections or elevated white count.
• Care should be taken to avoid contamination of samples with skin flora
• If filling serial samples from same syringe, fill aerobic(blue) tube first to draw out air in the needle before filling the anaerobic(orange) tube

Echocardiography

• Patients should undergo cardiac echo if staph aureus bacteremia is found to look for endocarditis

Management

• Uncomplicated MRSA with 14 days of IV vancomycin
• Gram negative bacteremia should be treated via empirical therapy based on suspected source
• Catheter associated infections
  • Short term catheters(<14 days) should be removed if cause of bacteremia, especially gram negative, staph aureus, enterococci, or mycobacteria
  • Long term catheters(>14 days) should be removed if patient is septic or bacteremia persists for 72+ hours

Resistance

• Extended spectrum beta lactam resistance - drugs of choice include those in the carbapenam family of antibiotics
• Carbapenam resistance - usually requires a combination regimen of two or more

See Also

• Sepsis (Main)