ICU learning pathway | Blood cultures

Blood Cultures
Session overview
Description
This session explains why blood cultures are clinically relevant and describes the procedure for taking blood culture samples.

By the end of this session you will be able to:

• Explain the clinical relevance of blood cultures
• List the indications for taking blood cultures
• Describe the technique for taking blood peripheral and central culture samples
• Describe the laboratory processes for analysing blood cultures
• List the causes of false positive and false negative results

Before commencing this session you should complete:

• Sepsis Resuscitation (001-0337)

In patients who have sepsis, approximately 50% have evidence of a bloodstream infection with bacteria, i.e. bacteraemia, or fungi, i.e. fungaemia [1](read details regarding the reference).

Sepsis carries a significant mortality of up to 50% [2](read details regarding the reference),[3](read details regarding the reference). Patients with a positive blood culture have been shown to have a greater severity of illness and a higher mortality [4](read details regarding the reference). Early appropriate antimicrobial therapy has been shown to decrease mortality [5](read details regarding the reference), therefore, IV antibiotics are recommended within 1 hour of the diagnosis of sepsis [6](read details regarding the reference).

Unfortunately, empirical antibiotic therapy may be ineffective against the causative organism in 20-30% of patients [7](read details regarding the reference),[8](read details regarding the reference). This is most frequently due to antibiotic resistance of the pathogen. Additionally, prolonged administration of broad-spectrum antibiotic therapy is associated with antibiotic resistance [9](read details regarding the reference).

Therefore, blood cultures are an imperative investigation in sepsis because the identification of a causative micro-organism in the blood is essential to guide the most appropriate antimicrobial therapy.