American Society for Microbiology

View all recommendations from this society

August 5 2020

Do not request routinely extended incubation of blood cultures in suspected endocarditis.

Extending incubation of routine blood cultures does not increase the recovery of clinically significant pathogens causing endocarditis. Five-day incubation,
using currently available media formulations and automated incubation and detection systems, is sufficient to recover the majority of true pathogens including HACEK organisms. Alternative methods (such as serology, molecular, targeted fungal or mycobacterial cultures, or tissue histopathology) should be utilized, when clinically indicated, for detection of rarely encountered, fastidious organisms (Bartonella, Coxiella, Mycobacterium, dimorphic fungi) not recovered using routine blood cultures. Occasional exceptions may be appropriate and should be reviewed in consultation with an infectious disease specialist.

These items are provided solely for informational purposes and are not intended as a substitute for consultation with a medical professional. Patients with any specific questions about the items on this list or their individual situation should consult their physician.
American Society of Microbiology in partnership with the Five Things Physicians and Patients Should Question

How The List Was Created

The American Society for Microbiology’s (ASM) list was developed under the leadership of the ASM’s Clinical and Public Health Microbiology Committee. The subject matter experts who identified the list and formulated the recommendations are laboratory directors at academic, commercial and public health laboratories and test utilization experts across the fields of microbiology and laboratory medicine. They worked together to identify a list of diagnostic and management decisions that have resulted in misuse of laboratory studies and resources. The five experts independently ranked the recommendations in order of priority and identified tests or procedures commonly used whose necessity should be questioned and discussed with patients. The experts formulated recommendations based on laboratory practice, evidence and an extensive review of the literature.

Five recommendations to address the most common clinical microbiology laboratory test misconceptions were written. They consist of diagnostic tests or treatments that are commonly ordered, expensive and have no evidence to illustrate its value and in some cases, may be potentially harmful to the patient. The recommendations, if instituted, would result in higher quality care, lower costs, and more effective use of our laboratory resources and personnel. The experts involved in this project are Sheldon Campbell, Marc Couturier, Omai Garner, Duane Newton, Preeti Pancholi and Linoj Samuel.

The recommendations were vetted and approved by ASM’s Clinical and Public Health Microbiology Committee.

The list has also been reviewed and approved by the ASCP Effective Test Utilization Committee.


Baron EJ, Scott JD, Tompkins LS. 2005. Prolonged Incubation and Extensive Subculturing Do Not Increase Recovery of Clinically Significant Microorganisms from Standard Automated Blood Cultures. Clin Inf Dis 41:1677-80.

Liesman RM, Pritt BS, Maleszewski JJ, Patel R. 2017. Laboratory Diagnosis of Infective Endocarditis. J Clin Micro 55:2599-2608.