Blood Cultures 7.3
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this is the invasion of bloodstream by virulent microorganisms.
this is the transient presence of bacteria or other microorganisms in the blood.
this is the presence of fungi in the blood stream.
this is the presence of viruses in the blood, characterized by malaise, fever, and aching of the back and extremities
septic shock is caused by what?
the release of toxins
what are five signs and symptoms of spetic shock?
- respiratory distress
- I.V. coagulation
- Renal failure
- tissue damage
this is one of the most important specimens.
healthy individuals have _______ blood.
what is the objective of blood cultures?
initiate growth of tastidious organisms
this involves very small numbers of organisms.
is septicemia more common in adults or infants?
this may depend on prompt recognition by bacteriologic means.
true or false
positive blood cultures reflect a variety of conditions and diseases
bacteremia is __________ in endocarditis, concontrolled infections, typhoid fever, and brucellosis.
in the early antibiotic era the primary concern was spesis due to what?
recently there is an increase in infections caused by gram negative bacteria such as what?
what are the two most frequent isolates from the pediatric population?
- haemophilus influenzae
- streptococcus pneumoniae
what is the mortality rate of septicemias?
this is reported in approximately 18% of proven septicemias, and associated with a higher mortality than unimicrobial infection
what three diseases are significant to gram negative septicemia?
- acute fulminating meningoccemia (waterhouse friderichsen syndrome)
- meningococci lipopolysaccharide endotoxin
- coagulation cascade activation (DIC)
which gram negative septicemia disorder is seen mainly in children under ten years old?
acute fulminating meningococcemia (waterhouse friderichsen syndrome)
what two broths can be used for blood culture media?
what amount of CO2 is used in blood culture media?
this allows the maximal yield of fastidious organisms and dispaces oxygen for anaerobic conditions.
what is the anticoagulant used in blood culture media?
sodium polyanethol sulfonate (SPS)
what are three advantages of sodium polyanethol sulfonate as an anticoagulant?
- inactivates certain antibiotics (aminoglycosides)
what is the disadvantage of sodium polyanethol sulfonate as an anticoagulant?
inhibitory for certain bacterial species
what four bacterial species are inhibited by sodium polyanethol sulfonate?
- peptostreptococcus anaerobius
- gardnerella vaginalis
- some neisseria strains
- S. monliformis
how is the inibitory action of SPS neutralized?
why is citrate and oxalate not used as an anticoagulant in blood cultures?
toxic for many organisms (GP)
why is heparin not used as an anticoagulant in blood cultures?
these help bacterial recovery, couteract nor bactericidal mechanism of blood and causes turbidity.
what are the three osmotic stabilizers in blood cultures?
what two things are used in blood cultures to absorb all antibiotics?
what is used in blood cultures to inactivate penicillin?
what is the purpose of a mycobacterial blood culture?
to detect mycobacterium
what are the two components of a mycobacterial blood culture?
- middlebrook 7H9
- automated system (Bactec MGIT)
what temperature should blood culture media be stored at?
scrupulous ____ preperation of venipuncture site is required.
antiseptic should remain on the skin for how long?
at least one minute
how long should 70% alcohol be applied after palpation of the site?
at least 30 seconds
how much blood should be collected for blood culture?
up to 20mL
how much blood should be in each culture bottle?
up to 10ml
what are four contaminants of blood cultures?
- stphylococcus epidermidis
- propionbacterium acnes
- bacillus species
how many samples should be collected in 24-48hrs to isolate?
when should you collect two samples from two sites at the same time?
if a patient is to be given antibiotics
______ culture is not enough to eliminate bacteremia
what is the minimal dilution to unmodified medium for blood culture?
how much blood should be drawn from an infant for blood culture?
- 1-5 ml depending on weight
- up to 4.5% of total blood volume
the sterile needle and syringe method is an example of what collection system?
open system collection
if using an open system the sample should be injected into culture bottle where?
using two syringes when collecting blood cultures reduces skin ______________.
when blood is taken directly from patient via sterile transfer set directly into bottle it is an example of what system?
how long can blood cultures be refrgerated for before testing?
at what temperature should blood cultures be incubated?
how long should routine aer/ana cultures be incubated for?
how long should SBE cultures be incubated for?
how long should brucella cultures be incubated for?
how long should fungi be incubated for? at what temp?
when should macroscopic/radiometric examination be performed?
durring first 6-8 hours then daily
what should aerobic cultures be subcultured to?
- Choc 5-105 CO2 for 24-48hrs
what medias should anaerobic cultures be subcultured to?
when do you subcultue a blood culture?
anytime culture turns positve macroscopically
what is a self-contained subculture system called?
what are the six portals of entry and their respective percentages?
- GU tract 25%
- respiratory- 20%
- Abscesses- 10%
- surgical wound- 5%
- misc sites- 10%
- uncertain sites- 25%
what are the six commonly isolated GPC's?
- S. epidermidis
- S. aureus
- Enterococcus spp
- strep pneumoniae
- viridans strep
- beta strep
what are the six commonly isolated GNR's?
- Enerobacter cloacae
- haemophilus influenzae
- E. coli
- P. aeruginosa
- K. pneumoniae
- proteus spp
what is the commonly isolated yeast?
what are the two commonly isolated anaerobes?
- B. fragillis
- Clostridium spp.
this is a group of fastidious GNR associated with infective endocarditis
what are the bacteria in the HACEK group?
- H. aphrobilus
- A. actinomycetecomitans
- C. hominis
- E. corrodens
- K. kingae
what are four findings on a positive blood culture?
- turbidity on medium
- growth on RBC sediment
- gas production
how long is a stock culture maintained for?
in what positive blood culture would you see uniform growth, turbidity or gas bubbles?
in what positive blood culture would you see no change?
in what positive blood culture would you see marked hemolysis, gas, and an unpleasant odor?
in what positive blood culture would you see turbidity balls and jelly-like coagulum?
in what positive blood culture would there be a greenish tint to the medium?
in what positive blood culture would there be marked hemolysis?
in what positive blood culture would there be turbidity, foul odor, and less gas?
in what positive blood culture would there be hemolyzed RBC's?
in what positive blood culture would there be a thick pellicle on media surface?
when is a blood culture considered negative?
after three to four sets
when do you report negative results?
after 7 days
what newer system monitors radio-labeled C14?
radiometric (BACTEC) system
what newer system monitors pH changes by colorimetric indicator?
this newer system puts concentrate onto plate media allowing a faster, better recovery.
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