Clinical and Laboratory Standards Institute guideline M47—Principles and Procedures for Blood Cultures provides recommendations for laboratory detection of bacteremia and fungemia using blood cultures. This guideline also includes recommendations for collecting, transporting, and processing specimens for blood culture and for interpreting and reporting results. Critical factors in the recovery of pathogens from blood specimens and related topics are also covered.

This guideline replaces the previous edition of the approved guideline, M47-A, published in 2007. Several changes were made in this edition, including: • Describing critical factors in recovering pathogens from blood specimens and providing guidance on selecting the best medium formulations, developing and applying breakpoints, and reporting results • Describing existing technologies capable of identifying the etiology of bloodstream infections (BSIs) and the benefits of using these technologies (including culture-independent methods) • Adding subchapters on special topics, including pediatric blood cultures, catheter-related BSIs, infective endocarditis, patients receiving antimicrobial therapy, and rare and fastidious pathogens • Including example quality assurance indicators for preexamination, examination, and postexamination activities • Removing descriptions of paper-based test ordering and results reporting, because the widespread use of electronic medical record systems has changed the way blood cultures are ordered and results are reported

This guideline is intended to provide recommendations to clinical microbiologists, other laboratorians (eg, pathologists, supervisors and/or managers, phlebotomists), and health care providers (HCPs) for recovering pathogens from the blood of patients with suspected bacteremia, mycobacteremia, or fungemia. It is also intended for administrators who develop institutional best practices. Specific recommendations for collecting, transporting, and processing blood culture specimens are also included. This guideline discusses the clinical significance of blood cultures, critical factors in recovering pathogens from blood specimens, selection of medium formulations and other laboratory practices, and development of interpretive criteria. It also discusses existing blood culture technologies and the relative benefits of these technologies. Special topics, including pediatric blood cultures; catheter-related bloodstream infections (CRBSIs); infective endocarditis; diagnostic testing for patients who are receiving antimicrobial therapy; rare and fastidious pathogens; and rapid diagnostic techniques, including culture-independent methods, are also covered. This guideline does not include procedures for pathogen ID and antimicrobial susceptibility testing (AST). For guidance on bacterial AST, refer to CLSI documents M02,11 M07,12 M11,13 M45,14 and M100.15 For guidance on fungal AST, refer to CLSI documents M27,16 M38,17 M44,18 M51,19 M60,20 and M61.21