Blood Cultures Flashcards
Why are blood cultures one of the most important tests in the lab?
- establish infectious etiology
- obtain pathogen for ID and susceptibility of antimicrobial therapy
- most important diagnostic tool for a physician
Bacteremia
cultivable bacteria in the blood stream. May be transient and in sequential but may also be life threatening
sepsis
bacteria reproducing infection of the bloodstream
- multiplies more rapidly than the immune system can clear
- can lead to: shock, multi organ system failure, dic death
- fever, chills, malaise, hypothermia, hyperventilation skin lesions, change in mental status, diarrhea
- sepsis is refered to as the intravascular inflammation
septic shock
- low blood pressure
- fever, acute respiratory distress, shock, renal failure, intravascular coagulation: lots of small clots, tissue destruction
- production of cytokines
- can be initiated by exotoxins or endotoxins
common pathogens found in blood cultures
- Staph. Aureus #1 pathogen
- Enteric GNRs, E. Coli mostly
- Coag Negative staph ( most common contaminant)
- streptococci pnemoniae but other strep
- Entrococcus ( common in UTIs and older women)
- Pseudomonas aeruginosa and other non fermenting GNR
intermittent bacteremia
when localized infections outside of the bloodstream seed bacteria into the blood stream
- example: undrained abscess, GU tract, Respiratory tract, billary tract
- no longer need to make separate collections to “catch” bacteria
continuous(sustained) bacteremia
results from constant shedding of bacteria into the bloodstream from an intravascular source
- ex. endocarditis, infected lined are most common source of continuous bacteremia
specimen collection
- essential to have a properly cleaned site ( this could introduce normal flora or other bacteria in as a contaminant)
- draw before antibiotics ( if drawn before the bacteria could already start to die and it may impede the cutlure process)
- venipuncture is prefered over a line draw ( a line could be contaminated and not be showing what is truly in the blood. Also venipuncture allows for good blood circulation.
- two sets of two bottles in a 24 hr period, no more than 3.( can drain to much blood and does not increase odds of ID if anymore than 3 really and only having one set or one bottle is not good statisitcally either. )
SPS
sodium polyanethol- sulfate: with SPS there is higher rate of recovery of organisms, but it can inhibit the growth of some organisms like N gonorrohea,n meningitidis, peptostreptococcus, g. vaginalis
- it acts as an anticoagulant, anticomplementary, antiphagocytic and interferes with some antimicrobial agents
polychromic septicemias
involve more than one bacteria
- likely acquired in hospital
- can arise from the bowl or multiple locations
- an be associated with tumors or other underlying diseases
- death is increased 2X with polymicrobic infections
BacTek
- fluorescence used to measure CO2 released by metabolizing bacteria
- gas permeable sensor on bottom of each vial
- computer reads and makes graph
- resins are used for antimicrobial removal
- uses plastic bottles
Veratrek
continuous monitoring - head space pressure monitors both 02 gas consumption and/or CO2, H2, and/N2 production
- redox 1 (aerobic) and Redox 2
- there is no resin for antimicrobial only high volume of broth for dilution
- approved for as low as .1
- redox 1 has a stir bar to continuously mix broth for optimal oxygenation
- glass bottles
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Postive blood culture media
- minimum of a blood and chocolate
- GNRs add mac
- mixed pea and a mac
- anerobes add a brucella and/or KV
unusual organisms seen in blood cultures
Fungi, brucells, mycobacterium, legionella, campylobaccter,
- Granulicatella, abiotriophia, streptococci ( Common cause of endocarditis)
- HACEK organisms ( haemophilus, actinobacillus, cardiobacterium, eikenella, kinella ( Fastidious GNRs)
one of two contaminants
Bacillus, Corynebacterium, propionibacterium, coag. neg. staph, virdians
