Blood Culture

Blood culture test is done to determine  infection presence in the blood. In normal conditions no bacteria or fungi are found in blood. Blood culture determines bacteria and fungi presence in the blood stream. Bacteria presence in blood is a serious condition because microorganisms may spread to whole body by the help of blood circulation. This is a life threatening condition and must be treated as soon as possible. Microorganism presence in blood is more  common in immunosuppressed patients like AIDS, cancer, diabetes, hemodialysis patients and may be caused by immunosuppressive treatments like chemotherapy or cortisone usage.

Purpose; why the blood culture test is done?blood-culture

Determination of the cause of infection that it is bacteria or fungi

Determination of the effective antibiotic for causative bacteria

Determination of the cause of the high fever

Identifying the bacteria type in sepsis in these kind of infections;

  • Meningitis
  • Kidney infections
  • Osteomyelitis
  • Pneumonia
  • Blooodstream infection
  • Lung infections
  • Abdominal infections

Blood culture is done to diagnose the cause of sepsis symptoms like;

  • Fever; higher than 38.3 ° C- 101 F
  • Low body temperature below than 36 ° C- 96.8 F
  • Elevated heart rate; higher than 90 beat per minutes
  • Rapid breathing, higher than 20 breaths per minute
  • Confusion
  • Decreased urine output
  • Difficulty breathing
  • Unconsciousness
  • Nausea
  • Seriously decreased blood pressure in severe sepsis cases
  • Organ failures (severe sepsis condition)
  • Low platelet count

How the blood culture test is done?

Procedure is similar with routine blood collection. Nurse will clean the site with an antiseptic like clorhexidine to prevent contamination and false positive results in blood culture. After cleaning she/he will insert the needle and collect 10 ml of blood inside a special blood culture bottle.  2 blood culture bottles are used for blood culture. Bottles contain a special liquid media-broth for bacteria growth as you can see in the picture.

Evaluation of blood culture test results

Bacteria and fungi need time to grow in culture media so blood culture test may take 1-2 days to result or more for fungi. Also antibiotic sensitivity test is done after positive results to find the correct-effective antibiotics for the bacteria.

Negative blood culture result

Negative result means your blood culture is normal , there are no bacteria or fungi detected in your blood.

Positive blood culture result

Positive result means some kind of bacteria are determined in the blood sample by infection or contamination, here are some bacteria and possible sources;

  • Staphylococcus epidermidis; may be sourced from contaminated IV catheters, heart valve prosthesis
  • Escherichia coli; indwelling catheters, perforated bowel, peritoneal infections, prostatitis
  • Staphylococcus aureus; abscess, decubitis ulcer, osteomyelitis, staphylococcal pneumonia, skin infections, soft tissue infections
  • Streptococcus pneumonia; alcoholoism, COPD ( chronic obstructive pulmonary disease), pneumonia, meningitis
  • Streptococcus pyogenes; skin infections, soft tissue infection, tonsillitis, pharyngitis
  • Alpha streptococcus; dental infections, gum disease
  • Pseudomonas aeruginosa; cystic fibrosis, infected burns-wounds
  • Candida species (fungal sepsis); burns, immunosuppressive therapy
  • Salmonella species; infected food and water


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