Bacteremia vs contaminated blood cultures: Difference between revisions
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==Background==
==Background==
*Staphylococcus aureus and Candida sp. isolated from the blood should never be considered a contaminant<ref>Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp</ref>
*[[Staphylococcus aureus]] and Candida sp. isolated from the blood should never be considered a contaminant<ref>Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp</ref>


==Suggestive of Contamination<ref>Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp</ref>==
==Suggestive of Contamination<ref>Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp</ref>==
#Typical commensal organisms of the skin flora '''in the abscence of''' an intravenous catheter
#Typical commensal organisms of the skin flora '''in the abscence of''' an intravenous catheter
##coagulase-negative Staphylococcal species
##coagulase-negative [[Staphylococcus]] species
##certain Streptococci
##certain Streptococci
##Gram-positive bacilli
##[[Gram-Positive]] bacilli
#Only 1 out of 2 or more blood cultures are positive
#Only 1 out of 2 or more blood cultures are positive
##Most commonly used when positive for coagulase-negative Staphylococcal species
##Most commonly used when positive for coagulase-negative [[Staphylococcal Species]]
#Antibiotic susceptibility pattern of one organism is different from the pattern of the other organisms in the same or subsequent set of cultures (as long as the organisms are of the same species)
#[[Antibiotic Susceptibility Pattern]] of one organism is different from the pattern of the other organisms in the same or subsequent set of cultures (as long as the organisms are of the same species)
##For example, if 2 sets of blood cultures are both positive for Staphylococcus epidermidis but one set is sensitive to a particular antibiotic while the other set is resistant to the same antibiotics, both sets are likely contaminated
##For example, if 2 sets of blood cultures are both positive for Staphylococcus epidermidis but one set is sensitive to a particular antibiotic while the other set is resistant to the same antibiotics, both sets are likely contaminated


Revision as of 07:00, 22 April 2014

Background

Suggestive of Contamination[2]

  1. Typical commensal organisms of the skin flora in the abscence of an intravenous catheter
    1. coagulase-negative Staphylococcus species
    2. certain Streptococci
    3. Gram-Positive bacilli
  2. Only 1 out of 2 or more blood cultures are positive
    1. Most commonly used when positive for coagulase-negative Staphylococcal Species
  3. Antibiotic Susceptibility Pattern of one organism is different from the pattern of the other organisms in the same or subsequent set of cultures (as long as the organisms are of the same species)
    1. For example, if 2 sets of blood cultures are both positive for Staphylococcus epidermidis but one set is sensitive to a particular antibiotic while the other set is resistant to the same antibiotics, both sets are likely contaminated

Risk Factors for Bacteremia[3]

  • Advanced age
  • Corticosteroids
  • Immunosuppressing medications (transplant patients, rheumatologic diseases, etc)
  • Chronic liver disease
  • Chronic renal failure (especially if on hemodialysis)
  • Hematological malignancies
  • HIV infection
  • Intravenous catheters
  • Intravenous drug use
  • Loss of skin integrity
  • Malnutrition and hypoalbuminemia
  • Neutropenia
  • Parenteral nutrition

Contamination Rates for Specific Organisms[4]

Organism False positives
Bacillus spp. >90%
Coag-negative Staphylococcus spp. >90%
Propionibacterium spp. >90%
Corynebacterium spp. >80%
Viridans-Group Streptococci 50%
Clostridium spp. 40%
Staphylococcus aureus spp. 25%
Enterococcus spp. 15%

See Also

Sources

  1. ↑ Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  2. ↑ Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  3. ↑ Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  4. ↑ Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
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