Blood Cultures and Septicemia Lecture

7/28/2019 Blood Cultures and Septicemia Lecture

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Why? Bacteraemia- bacterial in the blood stream (e.g.

cleaning teeth)

Septicaemia- infection of bloodstream Usually taken if patient has a fever

Antibiotics started after taking blood cultures ifpossible but if not use broad spectrum


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Source Usually another underlying infection

E.g urinary catheter, central line, meningitis

Then spreads to other organs via bloodstream Blood samples collected and cultured


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CollectionWhen patient spikes a fever

Most have paired bottles: aerobic and anaerobic

Approx 5-10mls each bottle Paediatric bottles available with smaller volumes

Incubated as soon as possible after collection


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Culture Most contain broth such as brain heart infusion or

tryptic soya as can grow a wide of organisms

Anaerobic bottles may have reducing agent or gas toensure anaerobic conditions

Mainly for bacteria- if fungi or TB suspected can getspecial bottles


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Types: non- automated

Bottles containing culturemedia

Add 5-10 mls patients blood

Incubate Subculture

Drawbacks- takes time to subculture

Contamination

Solution- provide mediaabove bottle


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Septicheck


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Non- automated: radiometric Early method- no longer used

Quicker detection

C14

Labelled glucose Produces radioactive CO2


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Automated: Different systems depending on which company has

produced it

Still look at production of CO2 but use a sensor- notradioactive

Continuous detection

Incubated 7 days

Positives indicated by a signal


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Examples: Bact-alert


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Bactec


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Collection http://www.youtube.com/watch?v=yz6GhnZE6KM
http://www.youtube.com/watch?v=yz6GhnZE6KMhttp://www.youtube.com/watch?v=yz6GhnZE6KMhttp://www.youtube.com/watch?v=yz6GhnZE6KM


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Identification of organisms Still need to subculture and carry out tests

Gram stain

Direct antibiotic sensitivity until organism isolated Have to check both bottles- quite often mixed

infection


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Anaerobes Quite often have anaerobic organism as well as aerobic

Particularly if following bowel surgery

Clostridia, bacterioides, fusobacteria


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Incidence of infections For some organisms (Staphylococcus aureus,Escherichia coli and glycopeptide-resistantenterococci) it is mandatory for hospitals to supplydata but for other species of bacteria data is suppliedon a voluntary basis (HPA data)


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The top ten monobacterial(HPA

2010) Number of cases organism26164 Escherichia13499 Staphylococcus,

coagulase negative9180 Staphylococcus aureus

7891 Streptococcus, non-

pyogenic4703 Klebsiella3997 Streptococcus,

pyogenic3498 Enterococcus3053 Pseudomonas1823 Proteus1558 Enterobacter


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Polymicrobial infections Similar organisms involved, although anaerobes also

feature in top 20

Sometimes up to 5 organisms may be involved Several organisms may mean contamination

Can involve fungal infections e.g. Candida


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Lab diagnosis Need to subculture from broth or bottle

If bottle has agar slope might be able to use colony

appearance Septicheck- which agar does it grow on?

Gram stain and direct sensitivity from broth

Identify as you would any pathogen

May be polymicrobial

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Blood Cultures and Septicemia Lecture