70 Questions
Which type of organism primarily infects immunosuppressed patients and those with serious or terminal illness?
Fungi
Which type of organism is particularly found in neonates receiving lipid-supplemented parenteral nutrition?
Fungi
Which type of organism can disseminate to all body organs?
Parasites
Which type of organism enters the blood via invasion of lymph nodes and other organs?
Fungi
Which type of organism primarily infects the target organ or cells?
Viruses
Which type of organism infects the endocardium and is most commonly caused by bacteria?
Bacteria
Which agar is used to culture Gram-negative bacteria?
MacConkey agar
Which organisms are considered probable contaminants in blood cultures?
Bacillus anthracis
Which condition is NOT consistent with sepsis based on clinical presentation?
Growth of skin flora
Which microorganisms may require alternative methods for diagnosis if they cause bloodstream infections?
Brucella spp.
What is the incubation period for Brucella spp. in blood cultures?
5-60 days
When should the physician be notified of positive culture results?
After 48 hours
Which factor is NOT a contributing factor to bloodstream infections?
Immunosuppressive agents
What is the recommended volume of blood to collect for blood cultures in adults?
10 to 20 mL per culture
What is the purpose of using anticoagulants in blood culture collection?
To prevent clotting
What is the recommended concentration of sodium polyanethol sulfonate (SPS) as an anticoagulant?
0.025% to 0.03%
What is the recommended number of blood cultures to obtain for optimum sensitivity in patients with endocarditis who have not received antibiotics?
Two blood cultures
What should phlebotomists do to prevent contamination during blood drawing?
All of the above
Which of the following is NOT a component of blood culture media?
Gelatin
What is the recommended blood to medium ratio in traditional dilution blood factor?
1:10
What is the purpose of venting the bottles in conventional blood cultures?
To enhance the growth of most aerobic bacteria
Which method combines liquid and solid medium in the same bottle for easy subculture?
Biphasic method
What is the purpose of instrument-based systems like BACTEC and BacT/ALERT?
To measure the production of CO2 by metabolizing microorganisms
How are positive blood cultures detected?
All of the above
Which term refers to the presence of bacteria in the bloodstream?
Bacteremia
What are the clinical manifestations of septicemia?
All of the above
Which bacteria are most commonly isolated in bloodstream infections?
Staphylococcus aureus, Streptococcus pneumoniae, Candida albicans
What is the purpose of using anticoagulants in blood cultures?
To prevent blood clotting
How are probable pathogens distinguished from contaminants in a blood culture?
By the type of bacteria isolated
Which term refers to the presence of bacteria in the blood?
Bacteremia
What is the suffix 'emia' derived from?
Greek word for 'blood'
Which of the following is a clinical manifestation of septicemia?
All of the above
Which bacteria is most commonly isolated in bloodstream infections?
Staphylococcus aureus
What is the process of specimen collection, handling, processing, and culturing for bacteremia detection called?
Blood culture
What are the major types of bloodstream infections?
Bacteremia and septicemia
Which organisms may require alternative methods for diagnosis if they cause bloodstream infections?
Brucella spp.
What is the incubation period for Brucella spp. in blood cultures?
5-60 days
Which agar is used to culture Gram-negative bacteria?
MacConkey agar
What is the purpose of venting the bottles in conventional blood cultures?
To allow aerobic growth of bacteria
Which type of organism infects the endocardium and is most commonly caused by bacteria?
Endocarditis
What is the recommended number of blood cultures to obtain for optimum sensitivity in patients with endocarditis who have not received antibiotics?
3 sets
Which type of organism primarily infects immunosuppressed patients and those with serious or terminal illness?
Opportunistic pathogens
What is the recommended volume of blood to collect for blood cultures in adults?
20-30 mL
What is the purpose of using anticoagulants in blood culture collection?
To prevent clotting
Which factor is NOT a contributing factor to bloodstream infections?
Regular hand hygiene
Which of the following is a clinical manifestation of septicemia?
Fever, hypothermia, chills
What is the purpose of using anticoagulants in blood culture collection?
To prevent clotting of the blood sample
Which type of organism primarily infects immunosuppressed patients and those with serious or terminal illness?
Opportunistic pathogens
What is the recommended number of blood cultures to obtain for optimum sensitivity in patients with endocarditis who have not received antibiotics?
3 sets
Which term refers to the presence of bacteria in the bloodstream?
Bacteremia
Which type of organism primarily infects immunosuppressed patients and those with serious or terminal illness?
Fungi
Which type of organism enters the blood via invasion of lymph nodes and other organs?
Parasites
What is the most common route of entry for bacteremia from an extravascular site?
Genitourinary tract
Which type of organism is particularly found in neonates receiving lipid-supplemented parenteral nutrition?
Fungi
Which type of organism primarily infects the endocardium and is most commonly caused by bacteria?
Bacteria
What is the recommended number of blood cultures to obtain for optimum sensitivity in patients with infective endocarditis who have not received antibiotics?
Three blood cultures are sufficient
What is the recommended volume of blood to collect for blood cultures in infants and children?
3-4 mL
What is the most commonly used anticoagulant in blood culture collection?
SPS
What is the purpose of venting the bottles in conventional blood cultures?
To prevent clotting
Which factor is NOT a contributing factor to bloodstream infections?
Prolonged survival of debilitated and seriously ill patients
Which of the following is a special culture/culturing condition for Brucella spp. in blood cultures?
Prolonged incubation period of 5-60 days
Which of the following is NOT a criterion to distinguish probable pathogens from contaminants in blood cultures?
Clinical presentation consistent with sepsis
Which of the following organisms is known as 'nutritionally variant' or 'satelliting' streptococci?
Streptococci
Which agar is used to culture Campylobacter in blood cultures?
CAMPY agar
Which of the following organisms is NOT considered a probable contaminant in blood cultures?
Staphylococcus aureus
Which method combines liquid and solid medium in the same bottle for easy subculture?
Biphasic method
What is the purpose of using anticoagulants in blood culture collection?
To prevent clotting of blood
Which condition is NOT consistent with sepsis based on clinical presentation?
Normal white blood cell count
What is the recommended concentration of sodium polyanethol sulfonate (SPS) as an anticoagulant?
1:10 ratio
Which agar is used to culture Gram-negative bacteria?
MacConkey agar
Study Notes
Blood Culture Methods and Techniques
- Gelatin can counteract the inhibitory action of SPS, but it may decrease the recovery of other organisms.
- Dilution blood factor: traditionally a 1:10 ratio of blood to medium, but new commercial media with additives may use a 1:5 ratio.
- Blood culture media typically contain nutrient broth, anticoagulant, and various additives.
- Some specialized media can absorb and inactivate antimicrobial agents, increasing the yield of microorganisms.
- Incubation conditions include temperature and time, with longer incubation required for certain microorganisms.
- Conventional blood cultures use commercially prepared bottles with low oxidation-reduction potential.
- Venting the bottles may be necessary for growth of obligate aerobes.
- Constant agitation during the first 24 hours enhances the growth of most aerobic bacteria.
- Bottles are examined daily for growth indicators like turbidity, gas, and discoloration.
- The biphasic method combines liquid and solid medium in the same bottle, allowing for easy subculture.
- Lysis centrifugation is a method used to detect microorganisms in body fluid specimens.
- Instrument-based systems like BACTEC and BacT/ALERT measure the production of CO2 by metabolizing microorganisms.
Handling Positive Blood Cultures:
- Positive blood cultures are detected through appearance, subculture plates, or instrument-based detection.
- Gram-stained smears and other tests are performed to identify and test antimicrobial susceptibility.
Blood Culture Methods and Techniques
- Gelatin can counteract the inhibitory action of SPS, but it may decrease the recovery of other organisms.
- Dilution blood factor: traditionally a 1:10 ratio of blood to medium, but new commercial media with additives may use a 1:5 ratio.
- Blood culture media typically contain nutrient broth, anticoagulant, and various additives.
- Some specialized media can absorb and inactivate antimicrobial agents, increasing the yield of microorganisms.
- Incubation conditions include temperature and time, with longer incubation required for certain microorganisms.
- Conventional blood cultures use commercially prepared bottles with low oxidation-reduction potential.
- Venting the bottles may be necessary for growth of obligate aerobes.
- Constant agitation during the first 24 hours enhances the growth of most aerobic bacteria.
- Bottles are examined daily for growth indicators like turbidity, gas, and discoloration.
- The biphasic method combines liquid and solid medium in the same bottle, allowing for easy subculture.
- Lysis centrifugation is a method used to detect microorganisms in body fluid specimens.
- Instrument-based systems like BACTEC and BacT/ALERT measure the production of CO2 by metabolizing microorganisms.
Handling Positive Blood Cultures:
- Positive blood cultures are detected through appearance, subculture plates, or instrument-based detection.
- Gram-stained smears and other tests are performed to identify and test antimicrobial susceptibility.
Test your knowledge on blood culture methods and techniques with this informative quiz. Explore topics such as media composition, incubation conditions, and specialized techniques for detecting microorganisms. Learn how to handle positive blood cultures and identify the organisms present. Perfect for medical professionals and laboratory technicians.
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