Blood Culture, Bacteria and Yeast

Optimum recovery of organisms will be achieved by adding up to a 10 mL maximum amount of blood. Published clinical studies have shown that the use of lower blood volumes may adversely affect recovery and/or detection times of organisms. False positivity may occur when the white blood cell count is high. Care must be taken to prevent contamination of the sample during collection and inoculation into the BD BACTEC vial. A contaminated sample will give a positive reading but will not indicate a relevant bacteremic organism. A determination of bacteremia must be made by the clinician based on such factors as type of organism recovered, occurrence of the same organism in multiple cultures, patient history, etc.

Limitations of BCID2 performance:
Blood culture media may contain non-viable organisms and/or nucleic acid at levels that can be detected by the BioFire BCID2 Panel leading to false positive test results. Typically, these false positives may present with more than one positive result because the BioFire BCID2 Panel may also detect the organism that is growing in the culture bottle. In the event of a BCID2 detection of any organism that is not reflected by Gram stain of the bottle, the following comment will be appended to the result:
“BCID2 has detected an organism not seen in the Gram stain of the bottle. This may be due to detection of an organism below the limit of sensitivity of the Gram stain but may also be due to the presence of non-viable organisms and/or nucleic acids in blood culture media.”
The Enterobacterales target is designed to react with species within the following families: Enterobacteriaceae, Erwiniaceae, Hafniaceae, Morganellaceae, Yersiniaceae, Pectobacteriaceae, and Budviciaceae including over 250 species of gram-negative, facultatively anaerobic rods and coccobacilli.
The E. coli assay cross-reacts with Shigella species (S. boydii, S. dysenteriae, S. flexneri, and S. sonnei); which are practically indistinguishable from E. coli by both phenotypic and genetic analyses but are only very rarely isolated from blood culture
The Klebsiella pneumoniae group includes three phylogroups classified as distinct species; K. pneumoniae, K. quasipneumoniae, and K. variicola. All three species have many of the same virulence factors and share biochemical and genetic similarities, which makes it difficult to distinguish K. quasipneumoniae and K. variicola from K. pneumoniae clinically or by standard culture methods. Species level identification will be reported upon culture and MALDI-ToF.
A negative BioFire BCID2 Panel result does not exclude the possibility of bloodstream infection.
In mixed cultures, the BioFire BCID2 Panel may not identify all targeted organisms in the specimen, depending upon the concentration of each target present. In particular, false negative results for Pseudomonas aeruginosa or Stenotrophomonas spp. may occur if another organism is present in the blood culture. Conversely, standard subculture methods may also not identify all organisms in a mixed culture, depending upon the concentration and growth characteristics of each organism present.
False negative test results may occur from sequence variants in the region targeted by the assay, the presence of inhibitors, technical error, sample mix-up, or an infection caused by an organism not detected by the panel.