Blood Cultures - Exam 9 Flashcards
Define bacteremia
The presence of bacteria in the blood.
Define fungemia
The presence of fungi in the blood.
Define septicemia
Bacteria is present in the blood, causing infection and reproducing within the bloodstream.
What are the three types of bacteremia?
Transient, intermittent and continuous
What type of bacteremia is described?
Organisms comprising of normal flora are introduced into the blood.
Transient bacteremia
What type of bacteremia is described?
Organisms are released into the blood at a fairly constant rate and are continuously present in the blood with or without symptoms.
Continuous bacteremia
What type of bacteremia is described?
Bacteria from an un-drained infected site are released into the blood spasmodically.
Intermittent bacteremia
When does septicemia occur?
When bacteria and their toxins multiply - often at rates that exceed removal by phagocytosis.
The following are symptoms of what?
Fever, chills, malaise, tachycardia, hyperventilation, and toxicity
Septicemia
What are the four major groups of microbes found circulating in blood during disease?
Bacteria, fungi, parasites, and viruses
What are the two types of fungus most often seen circulating in the blood during disease?
C. albicans (account for 8-10% of all nosocomial bloodstream infections.
Malassezia furfur (seen in patients receiving lipid supplements/ most often neonates)
What are the three viruses most often seen circulating in the blood during disease?
Epstein Barr (invades lymphs), CMV (invades lymphs, monocytes, and PMNs), and HIV (invades certain T-lymphs)
What are the four most common parasites found circulating in the blood during disease?
Plasmodium, Trypanosoma, Babesia, and Microfilariae (Loa Loa, Brugia, and Wuchereria)
When is the ideal time to collect a blood culture?
30-45 min before a temperature spike
What is acute febrile illness?
Rapid onset fever along with symptoms, can be caused by a wide range of pathogens
What is empiric antibiotic therapy?
Antibiotic therapy given within the first 24 hours of admission
When might empiric antibiotic therapy be indicated?
When a patient has an acute febrile illness
What are two of the main diseases that may cause acute febrile illness?
Meningitis and bacterial pneumonia
What are two instances where emergency surgery may be necessary for a patient suffering from acute febrile illness?
If the patient has suppurative arthritis or osteomyelitis
Why do you need extra sets of blood culture bottles when treating a patient with fever of unknown origin?
To ensure that you are detecting the infectious agent and not a contaminant from equipment or natural body flora
In the case of a fever with an unknown origin, how many blood cultures should be drawn initially and what is the interval between sets?
2 blood cultures should be drawn initially with an interval of 45-60 minutes, 2 additional sets can be then drawn 24-48 hours later
What are interval draws used for?
To aid in determining if a continuous or intermittent seeding of the blood exists
In the case of infective endocarditis, how many blood cultures should be drawn initially and in what time frame?
3 blood cultures in the first 1-2 hours of evaluation (3 separate venipunctures - should be done before therapy begins)
In the case of infective bacterial endocarditis, how many blood cultures should be drawn and in what time frame? What do you do if those are negative?
3 blood cultures within the first 24 hours, with 30 minutes between each
Obtain 2 more sets on subsequent days
What are the 5 groups of bacteria that may be a common cause infective endocarditis?
- Viridans Strep (normal oral flora - gains entry through gingivitis, periodontitis and dental manipulation)
- Nutritionally Variant Strep
- HACEK group
- Enterococcus
- S. aureus (most common cause of infective endocarditis)
Who is at a higher risk of having infective endocarditis from the Viridans Strep group?
IV drug users because of the use of spit to “clean” the injection site
What are the 4 groups of bacteria commonly associated with IV catheter bacteremia?
- S. epidermidis (produces biofilm made of complex sugars that adhere to catheter surface)
- Other Coag Neg Staph
- S. aureus
- Enterobacteriaceae
Bacteremia from extravascular sites of infection can come from…
Wounds, soft tissue, respiratory, CSF, and GU tract
Which organisms are the common cause of bacteremia from a wound infection?
Anaerobes, P. aeruginosa, and Group A Strep
Which organisms are the common cause of bacteremia from a soft tissue infection?
Anaerobes, Coag Negative Staph, P. aeruginosa, Group A Strep, and S. aureus
Which organisms are the common cause of bacteremia from a respiratory infection?
H. flu and S. pneumoniae
Which organisms are the common cause of bacteremia from a CSF infection?
H. flu, Listeria, N. meningitidis, S. pneumoniae, and S. aureus
Which organisms are the common cause of bacteremia from a GU tract infection?
Enterobacteriaceae, and C. albicans
What is the hospital standard for contamination rates?
3%
How do you sterilize a venipuncture site for blood culture collection?
Cleanse with Chloroprep in a concentric fashion for 30 seconds and do not touch the skin after (even with gloves )
What is the recommended volume for an adult blood culture bottle?
8-10 mL per bottle (percentage yield of positive culture drops if less than 10 mL per bottle is obtained)
What is the recommended volume for each blood culture bottle for child?
1-5 mL proves to be satisfactory
Which bottle should be drawn first if there is a difficult person to draw?
The aerobic bottle
What is the ratio for ideal recovery?
1:10
What does Trypticase soy broth/Brain heart infusion broth contain? What type of bacteria is this media good for?
Soybean and casein digests - good for aerobic bacteria
What kind of organisms is Thioglycolate broth most ideal for?
Anaerobic bacteria
What is Sodium Polyanetholsulfonate (SPS) media good for?
Preventing coagulation without harming the bacteria, inactivating neutrophils and certain antibiotics, and inhibiting the growth of certain bacteria.
What types of bacteria does SPS inhibit?
P. aeruginosa, GC, N. meningitidis, and G. vaginalis
What organism is Castaneda double medium good for recovering?
Brucella
What is the biphasic technique, what are the conditions for incubation?
When the blood culture bottle contains both solid and liquid media.
Needs to be incubated in 5-10% CO2 @ 35-37C for 30 days and tipped every 48 hours to inoculate agar surface, also needs to be subcultured at least twice a week.
What is Fletchers medium and what organisms is it good for recovering?
Semi-solid media with rabbit serum and SPS.
It is good for recovering Leptospira.
What are the incubation conditions for Fletchers medium, how and when is it examined?
Incubated in the dark @30C for 28 days. Examined weekly by darkfield microscopy
What are the incubation conditions for blood culture bottles?
Incubated @35C and held for 5 days
What should be done immediately if a blood culture bottle is suspected to be positive?
A Gram stain and a follow up with the provider if the Gram stain is positive
What are the three ways blood culture bottles are examined?
Macroscopically, radiometrically, and fluorometrically
What are the three blood culture systems we should be familiar with?
BACTEC FX, ISOLATOR, and SEPTI-CHEK
What are the common macroscopic observations of Gram Negative Bacilli in blood culture bottles (usually Enterics)?
Medium above red cell layer becomes turbid and gas bubbles are present
What are the common macroscopic observations of Pneumococcus and Meningococcus in blood culture bottles?
Turbidity and a greenish tint to the medium
What are the common macroscopic observations of Streptococcus in thioglycolate media?
Strep appears as cotton ball colonies on top of the sedimented red cells
What are the common macroscopic observations of Staphylococcus in blood culture?
Staph frequently produces a large jelly-like coagulum and appears turbid
What are the common macroscopic observations of Bacillus in blood culture?
Lysed RBCs and a thick film on the surface
What are the common macroscopic observations of Clostridium in blood culture?
Produces a large head of has and lysed RBCs
What are the common macroscopic observations of Bacteroides in blood culture?
Less gas than Clostridium and a foul odor
What are the common macroscopic observations of H. flu in blood culture?
Little or no change in the media
