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Questions and Answers
What is a probable contaminant when interpreting positive blood culture results?
In interpreting blood culture results, what indicates the presence of a significant pathogen?
What is a guideline for distinguishing significant pathogens from contaminants in blood cultures?
What technology is increasingly used as a rapid alternative to culture-based methods in bacteriology laboratories?
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What is the main advantage of automated blood culture systems over manual blood culture methods?
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In automated blood culture systems, growth is typically detected by sensors measuring the levels of which gas?
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In the processing of positive blood cultures, what is the recommended next step after identifying an organism through Gram staining?
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Which type of media is NOT typically used for subcultures from positive blood cultures to support the growth of most bacteria?
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Why is the identification of an organism in blood culture not included in the diagnostic criteria for sepsis?
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What is the recommended sampling method for identifying the causative microorganism in sepsis using culture-based methods?
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Why does empirical antimicrobial therapy reduce the sensitivity of blood cultures drawn shortly after treatment initiation?
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What does a blood culture typically consist of?
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Study Notes
Blood Culture Interpretation
- A probable contaminant in blood culture results is skin flora, such as coagulase-negative staphylococci, Bacillus, Corynebacterium, and Propionibacterium.
Identifying Significant Pathogens
- The presence of a significant pathogen in blood culture results is indicated by the growth of a single pathogenic species in multiple bottles or the growth of multiple pathogenic species in a single bottle.
Distinguishing Significant Pathogens from Contaminants
- A guideline for distinguishing significant pathogens from contaminants in blood cultures is to consider the patient's clinical status, the type of organism isolated, the growth of the organism in multiple blood culture bottles, and the absence of apparent contamination.
Rapid Alternatives to Culture-Based Methods
- Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) is increasingly used as a rapid alternative to culture-based methods in bacteriology laboratories.
Automated Blood Culture Systems
- The main advantage of automated blood culture systems over manual blood culture methods is the ability to continuously monitor blood culture bottles for microbial growth.
- In automated blood culture systems, growth is typically detected by sensors measuring the levels of CO2.
Processing Positive Blood Cultures
- After identifying an organism through Gram staining, the recommended next step is to perform subcultures on appropriate media for further identification and susceptibility testing.
Subculture Media
- A type of media NOT typically used for subcultures from positive blood cultures is a fungus-specific medium, as it does not support the growth of most bacteria.
Sepsis Diagnosis
- The identification of an organism in blood culture is not included in the diagnostic criteria for sepsis because it may not be present in all cases of sepsis.
Sampling for Sepsis Diagnosis
- The recommended sampling method for identifying the causative microorganism in sepsis using culture-based methods is to collect two to three sets of blood cultures from different venipuncture sites.
Impact of Antimicrobial Therapy
- Empirical antimicrobial therapy reduces the sensitivity of blood cultures drawn shortly after treatment initiation because it can clear the bloodstream of the causative microorganism.
Blood Culture Composition
- A blood culture typically consists of a blood sample mixed with growth medium in a specialized bottle.
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Description
Learn about the challenges faced by clinicians and microbiologists in interpreting positive blood culture results, including distinguishing contaminants from pathogens. Explore guidelines for interpreting the significance of growth of bacteria like CoNS, Viridans streptococci, and Corynebacteria in blood cultures.
