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Blood Culture 

  • Author: Christopher P Kellner, MD; Chief Editor: Thomas M Wheeler, MD  more...
Updated: Aug 01, 2014

Reference Range

The reference range for blood culture is no growth.



True infection is almost always present if the culture is positive for one of the following organisms:[1, 2]

  • Streptococci (non-viridans)
  • Aerobic and facultative gram-negative rods[3]
  • Anaerobic cocci
  • Anaerobic gram-negative rods
  • Yeast

Negative growth does not rule out infection.

Suspect contamination if only one of several cultures is positive, if detection of bacterial growth is delayed (≥5 d), or if multiple organisms are isolated from one culture.[4]

Common contaminants include the following:

  • Staphylococcus epidermidis[5]
  • Bacillus species
  • Propionibacterium acnes
  • Corynebacterium species
  • Clostridium perfringens
  • Viridans Streptococcus
  • Candida tropicalis

Collection and Panels

Specifics for collection and panels are as follows:

  • Specimen type - Whole blood
  • Container - Culture bottles (one aerobic and one anaerobic) for blood and green-top tube (heparin) for fungus and mycobacteria (if warranted by clinical suspicion)
  • Collection method - Venipuncture
  • Specimen volume - Adults: 10-20 mL per culture set; Pediatric patients: 1.0-3.0 mL

Other instructions are as follows:

  • Collect specimens as soon as possible after onset of chills or fever and before beginning antibiotic therapy.
  • Use aseptic technique (eg, clean venipuncture sites and culture vial tops with 2% chlorhexidine/70% isopropyl alcohol swabs before collection).
  • Draw 2-3 sets of cultures from separate sites at least 30-60 min apart (no more than 4 sets per 24-hour period).
  • Do not draw from IV catheter unless other sites unavailable.
  • Related tests - Complete blood count (CBC), urine culture, bacterial wound culture, gram stain, CSF analysis, fungal tests, susceptibility testing, sputum culture



Blood cultures are used to identify microorganisms in the blood and to assist in guiding antimicrobial therapy. Common sources of bacteremia include the following:[6, 7]

  • Genitourinary tract
  • Respiratory tract
  • Abscesses
  • Surgical wounds
  • Biliary tract
  • Prosthetic cardiac valves


Indications for blood culture include symptoms of bacteremia or sepsis, such as the following:

  • Fever, chills
  • Rapid breathing and heart rate
  • Confusion
  • Severe hypotension
  • Decreased urine output
Contributor Information and Disclosures

Christopher P Kellner, MD Resident Physician, Cerebrovascular Research Laboratory, Department of Neurological Surgery, Columbia University Medical Center, New York Presbyterian Hospital

Christopher P Kellner, MD is a member of the following medical societies: American Association of Neurological Surgeons, American Medical Association, Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Chief Editor

Thomas M Wheeler, MD Chairman, Department of Pathology and Immunology, WL Moody, Jr, Professor of Pathology, Professor of Urology, Baylor College of Medicine

Thomas M Wheeler, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for Cancer Research, American Medical Association, American Society for Clinical Pathology, American Society of Cytopathology, American Thyroid Association, American Urological Association, College of American Pathologists, United States and Canadian Academy of Pathology, International Society of Urological Pathology, Harris County Medical Society

Disclosure: Received stock from PathXL for medical advisory board. for: PathXL, Inc.


Judy Lin, MD

Disclosure: Nothing to disclose.

  1. Wallach J. Interpretation of Diagnostic Tests. 6th ed. New York: Little, Brown; 1996. 717.

  2. Martinez RM, Bauerle ER, Fang FC, Butler-Wu SM. Evaluation of three rapid diagnostic methods for direct identification of microorganisms in positive blood cultures. J Clin Microbiol. 2014 Jul. 52(7):2521-9. [Medline].

  3. Hazelton BJ, Thomas LC, Unver T, Iredell JR. Rapid identification of Gram-positive pathogens and their resistance genes from positive blood culture broth using a multiplex tandem RT-PCR assay. J Med Microbiol. 2013 Feb. 62:223-31. [Medline].

  4. Washer LL, Chenoweth C, Kim HW, Rogers MA, Malani AN, Riddell J 4th, et al. Blood culture contamination: a randomized trial evaluating the comparative effectiveness of 3 skin antiseptic interventions. Infect Control Hosp Epidemiol. 2013 Jan. 34(1):15-21. [Medline].

  5. Sharma P, Satorius AE, Raff MR, Rivera A, Newton DW, Younger JG. Multilocus Sequence Typing for Interpreting Blood Isolates of Staphylococcus epidermidis. Interdiscip Perspect Infect Dis. 2014. 2014:787458. [Medline]. [Full Text].

  6. McPherson RA, Matthew R. Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia: Elsevier Saunders; 2011. 254-5.

  7. Wallach J. Interpretation of Diagnostic Tests. 6th ed. New York: Little, Brown; 1996. 717.

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