Bacteremia vs contaminated blood cultures: Difference between revisions
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**Coagulase-negative [[Staphylococcus]] species | **Coagulase-negative [[Staphylococcus]] species | ||
**Certain [[Streptococci]] | **Certain [[Streptococci]] | ||
**[[Gram-Positive]] bacilli | **[[Gram-Positive]] bacilli (rods) | ||
*Only 1 out of 2 or more blood cultures are positive | *Only 1 out of 2 or more blood cultures are positive | ||
**When positive for coagulase-negative [[Staphylococcal Species]] | **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 | ||
==Risk Factors for Bacteremia<ref name="perez"></ref>== | ==Risk Factors for Bacteremia<ref name="perez"></ref>== | ||
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*Intravenous drug use | *Intravenous drug use | ||
*Loss of skin integrity | *Loss of skin integrity | ||
*Malnutrition and hypoalbuminemia | *Malnutrition and [[hypoalbuminemia]] | ||
*Neutropenia | *Neutropenia | ||
*Parenteral nutrition | *Parenteral nutrition | ||
| Line 32: | Line 32: | ||
! Organism !! False positives | ! Organism !! False positives | ||
|- | |- | ||
| Bacillus spp. || >90% | | [[Bacillus]] spp. || >90% | ||
|- | |- | ||
| Coag-negative [[Staphylococcus]] spp. || >90% | | Coag-negative [[Staphylococcus]] spp. || >90% | ||
|- | |- | ||
| Propionibacterium spp. || >90% | | [[Propionibacterium]] spp. || >90% | ||
|- | |- | ||
| Corynebacterium spp. || >80% | | [[Corynebacterium]] spp. || >80% | ||
|- | |- | ||
| [[Viridans-Group Streptococci]] || 50% | | [[Viridans-Group Streptococci]] || 50% | ||
|- | |- | ||
| Clostridium spp. || 40% | | [[Clostridium]] spp. || 40% | ||
|- | |- | ||
| [[Staphylococcus aureus]] spp. || 25% | | [[Staphylococcus aureus]] spp. || 25% | ||
|- | |- | ||
| Enterococcus spp. || 15% | | [[Enterococcus]] spp. || 15% | ||
|} | |} | ||
Latest revision as of 15:09, 21 May 2020
Background
- Staphylococcus aureus and Candida sp. isolated from the blood should never be considered a contaminant[1]
Suggestive of Contamination[1]
- Typical commensal organisms of the skin flora in the abscence of an intravenous catheter
- Coagulase-negative Staphylococcus species
- Certain Streptococci
- Gram-Positive bacilli (rods)
- Only 1 out of 2 or more blood cultures are positive
- 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)
- 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[1]
- 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[1]
| 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
References
- ↑ 1.0 1.1 1.2 1.3 Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp