From the Guidelines
Gram-positive cocci in chains can indeed be contaminants in blood cultures, particularly if other blood cultures drawn at the same time are negative, suggesting contamination with skin flora. This consideration is crucial in the context of preventing the spread of vancomycin resistance, as highlighted in the recommendations for preventing the spread of vancomycin resistance by the Hospital Infection Control Practices Advisory Committee (HICPAC) 1. When encountering gram-positive cocci in chains in blood cultures, it is essential to differentiate between contamination and true bacteremia, which may require treatment. Factors to consider include the number of positive blood culture sets, the patient's clinical presentation, and the presence of risk factors for bacteremia.
- Common contaminants include skin flora such as coagulase-negative staphylococci, which can be introduced into blood samples during collection.
- The identity of the organism, once fully characterized, also plays a significant role in determining the appropriate course of action.
- Empiric treatment with antibiotics may be initiated in critically ill patients, but the decision to continue or discontinue should be based on complete microbiology results and the clinical picture.
- Training of phlebotomists and other personnel to minimize microbial contamination of specimens is vital, as emphasized in the HICPAC recommendations 1, to prevent inappropriate administration of vancomycin and other antibiotics.
From the Research
Gram-Positive Cocci in Chains as Contaminants in Blood
- Gram-positive cocci in chains can be a contaminant in blood, but they can also be a cause of infection, particularly in cases of streptococcal or enterococcal bacteremia 2, 3.
- The presence of gram-positive cocci in chains in blood cultures can be evaluated using diagnostic tests such as the Verigene Gram-positive blood culture assay, which has an overall concordance of 89.7% with culture 2.
- A treatment algorithm can be developed based on the identification of gram-positive cocci in chains in blood cultures, allowing for targeted treatment of infections caused by these organisms 2.
- In some cases, gram-positive cocci in chains may be resistant to commonly used antibiotics, such as vancomycin, and may require treatment with alternative agents, such as linezolid, daptomycin, or tigecycline 4, 5, 6.
- Rapid identification of gram-positive cocci in chains in blood cultures is important for early reporting and administration of proper antimicrobial treatment, and can be achieved using diagnostic tests such as latex agglutination tests or the tube coagulase test 3.