Is there a protocol for withdrawing blood from one patient for bacterial blood culture, and is it necessary to collect samples from at least two different venipuncture (venous puncture) sites?

From the Guidelines

Yes, it is recommended to withdraw blood from two different sites for bacterial blood culture to help with interpretation of results and identification of skin commensals. The protocol for collecting blood for bacterial blood cultures involves collecting at least two sets, each from a separate site, with proper skin preparation and filling of blood culture bottles 1.

Key Points for Blood Culture Collection

• Collect blood cultures via peripheral venipuncture with appropriate skin preparation to mitigate contamination.
• Use a dedicated venipuncture team if possible.
• Properly fill blood culture bottles with 10 mL of blood per bottle.
• Include at least one aerobic and one anaerobic bottle in each set.
• Collect at least two sets from separate sites to distinguish true bacteremia from contamination 1.
• Collection of blood cultures should not delay the start of antimicrobial therapy in febrile ICU patients if such therapy is indicated, with a delay of less than 45 minutes 1.

Importance of Two-Site Collection

The two-site approach is crucial for distinguishing true bacteremia from contamination, as the same organism growing in both sets suggests a true infection rather than skin contamination 1. This approach improves diagnostic accuracy by reducing false positives from skin contaminants and increases the overall yield of detecting bacteremia.

Collection Procedure

When collecting the samples, proper skin antisepsis is crucial, and the use of sterile gloves is recommended to prevent contamination 1. The timing between draws can be simultaneous or within a short period, though simultaneous collection from different sites is preferred when sepsis is suspected.

From the Research

Blood Culture Protocols

• The protocol for withdrawing blood from one patient for bacterial blood culture involves obtaining two sets of blood culture bottles, each set containing one aerobic and one anaerobic bottle, from separate peripheral sites 2.
• The American Society of Microbiology recommends that blood cultures should be obtained from two separate venipuncture sites, with at least 2 blood cultures should be obtained from separate peripheral sites 2.
• A study comparing single-site sampling (SSS) and multisite sampling (MSS) protocols found that SSS resulted in higher positivity rates, higher sample volume, and fewer solitary blood culture sets 3.

Sampling Sites

• Blood cultures should not be obtained from arterial catheters, as they are not a reliable sampling site and may result in continuous contamination of the catheter system 4.
• Obtaining blood cultures from central lines can lead to higher contamination rates and may result in false-positive cultures, which can lead to unnecessary antibiotic treatment and increased healthcare costs 5.
• Venipuncture is the recommended method for obtaining blood cultures, and phlebotomists should be trained in aseptic technique to minimize contamination rates 5.

Best Practices

• Blood cultures should be obtained before antibiotic therapy begins to maximize their utility 2.
• Clinical prediction rules, such as the Shapiro decision rule, may be useful in predicting true bacteremia, but clinical gestalt should take precedence 2.
• The sample volume for blood cultures should be at least 7 mL per bottle, and ideally 8-12 mL 3.