Best practices dictate that blood culture bottles should always be sent to the lab as soon as possible after blood collection for optimal results.
The method used detects aerobic and anaerobic bacteria as well as Candida and Cryptococcus. For adult patients, submit 15-20 mL from each of two separate sites. Culture of 30-40 mL per septic episode, not per fever spike, is sufficient to detect 99.9% of cases of sepsis in adults. For optimum diagnosis of sepsis, sample 3-4 sites only on the first day of a septic episode. Cultures on subsequent days are of minimal diagnostic value. If peripheral access is poor, one peripheral sample should be accompanied by a 15-20 mL line-drawn specimen.
less than 5 mL in adult bottle
greater than 10 mL in adult bottle
only an anaerobic bottle received
pediatric bottle used on an adult patient
routine blood cultures accompanying approved quantitative blood cultures
Susceptibility testing is routinely performed except on organisms that are likely skin or air contaminants including single positive cultures growing coagulase-negative Staphylococcus.
PCR for MRSA and MSSA is routinely performed on positive blood cultures with gram-positive cocci in clusters. The assay cannot detect MSSA if MRSA is present.
Filamentous Fungus blood cultures should be drawn when Malassezia furfur or dimorphic fungi, e.g. Histoplasma capsulatum, are suspected or in the presence of negative routine blood cultures. See Culture, Blood, Filamentous Fungi entry.
For fastidious bacteria, contact the UWHC Director of Microbiology at (608) 263-4445 to discuss appropriate testing methods. If mycobacteria or cytomegalovirus is suspected, see specific entries. UWHC/UWMF providers please refer to the UConnect intranet site. See Best Practices for Blood Culturing.