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Dr.T.V.Rao MD
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What is a Blood Culture?
A blood culture is alaboratory test in
which blood isinjected into bottleswith culture media todetermine whether
microorganisms haveinvaded the patientsbloodstream.
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Need for Blood
Culture?No microbiological test is more essential to the
clinician than the blood culture. The findingof pathogenic microorganisms in a patients
bloodstream is of great importance in terms
of diagnosis, prognosis, and therapy.
- L. Barth Reller, Clin. Infect. Diseases, 1996
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Blood Culture is done to
Detect Infectious Diseases Blood culture is a
microbiological culture of
blood. It is employed todetect infections that arespreading through thebloodstream (such asbacteremia, septicemia
amongst others). This ispossible because thebloodstream is usually asterile environment
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A clinically suspected infection is ultimatelyconfirmed by isolation or detection of theinfectious agent. Subsequent identification of the
microorganism and antibiotic susceptibility testsfurther guide effective antimicrobial therapy.Bloodstream infection is the most severe form ofinfection and is frequently life-threatening, and
blood culture to detect circulatingmicroorganisms has been the diagnosticstandard.
Proof in Blood borneInfection
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Bacteremia presence of bacteria in
blood stream
Some conditions have a period of bacteremiaas part of the disease process (ex.
Meningitis, endocarditis)
Septicemia bacteremia plus clinicalsigns and symptoms of bacterialinvasion and toxin production
Definitions
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Definitions (contd)
Primary Bacteremiablood stream bacterialinvasion with no
preceding or simultaneoussite of infection with thesame microorganism
Secondary Bacteremiaisolation of a
microorganism fromblood as well as othersite(s)
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Bacteremia and Fungemia Episodes
Transient
Comes and goes
Usually occurs after aprocedural manipulation(ex. Dental procedures)
Intermittent
Can occur fromabscesses at some bodysite that is seedingthe blood
Continuous
Bacteremia
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Warm shockfever, increased pulse,
hyperventilation, and warm, dry flushed skin
Cold shock
decreased blood pressure, increasedpulse, and rapid, shallow respirations
Septic chock
Hemodynamic changes, decreased tissue perfusionand compromised organ & tissue function
Mortality 40% to 50%
Bacteremia Complications
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Bacteremia/Septicemia RiskFactors
Immunocompromis
ed patients
Increased use of
invasive procedures
Age of patient
Administration of
drug therapy
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Sources of Bacteremia
Spread Pericarditis and
Peritonitis
Pneumonias Pressure sores
Prosthetic medicaldevices
Total hip replacement
Skeletal system
Skin and soft tissue
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Needs optimal Methods for Diagnosis ofBlood Borne Pathogens
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Blood Collection
Aseptic collectionprocedure is critical
Amount of blood 1:10 ratio of blood to
broth
Younger than 10 years
1 ml of blood for
every year of life
Over 10 years 20 ml
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Blood Collection
Frequency of Collection
Depends if bacteremia is
transient, intermediate
or continuous
Number of cultures
collected are usually
inversely related to the
type of bacteremia Usually x3 from different
body sites
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Conventional Broth Systems
One aerobic bottle and one anaerobic bottle per blood
collectionAerobic broth contains soybean casein digest broth,
Tryptic or trypticase soy broth, Brucella agar orColumbia broth base
Anaerobic broth is usually the same as aerobic withaddition of 0.5% cysteine in an aerobic environment
Must be subcultured and gram stained manually
Blood Culture Methods
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Venipuncture is the process of obtaining
intravenous access for the purpose of intravenoustherapy or obtaining a sample of venous blood. This
procedure is performed by medical laboratoryscientists, medical practitioners, some EMTs,paramedics phlebotomists and other nursing staff.Venipuncture is one of the most routinely performed
invasive procedures and is carried out for tworeasons, to obtain blood for diagnostic purposes or tomonitor levels of blood components (Lavery & Ingram2005).
Venipuncture
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Phlebotomy Definition
phlebotomy (fli)noun the act or practice
of bloodletting as atherapeutic measure
Phlebotomy fromGreek words, phlebo,relates to veins, tomy,
relates to cutting.Opening a vein to
collect blood
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Properly labelled sample is essential so that
the results of the test match the patient. Thekey elements in labelling are:
Patient's surname, first and middle.
Patient's ID number.
NOTE: Both of the above MUST match the
same on the requisition form.Date, time and initials of the phlebotomist
must be on the label of EACH tube.
LABELING THE SAMPLE
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Gloves will be worn in accordance withstandard precautions.
Appropriate verification of the patient'sidentity, by means of an armband or areaspecific procedure, will occur before thespecimen collection.
Cultures should be drawn before
administration of antibiotics, if possible.??? blood cultures should be drawn from lines,
but should be drawn viavenipuncture.
Principles for Collection
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Chlorhexidine swabs (1-2 packages) Alcohol swabs Blood culture bottles (2 bottles per set) 2 syringes (adult: 20 cc, paediatric: 5 cc) 2 needles (adult: 22 gauge or preferably larger butterfly
or standard needle; pediatric: 25 or 23 gauge butterfly orstandard needle)
Gloves (sterile &nonsterile) Tourniquet
Sterile gauze pad Adhesive strip or tape Self-sticking patient labels Plastic zip lock specimen bags
What Materials We need
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The requisitions form should be completelyfilled out, and the requisition must indicate
the tests ordered.
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Self Protection
A few ways to make sure yourrole in the collection process is
carried out with efficiency,orderliness and safety
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Steps 1 3, Check, Explain, Wash
1.Identify the patient
2.Explain theprocedure to thepatient.
3.Wash hands withsoap and water withfriction for 15 seconds
or use alcohol basedhand rub
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Materials Chlorhexidine swabs (1-2 packages) Alcohol swabs Blood culture bottles (2 bottles per set)
2 syringes (adult: 20 cc, paediatric: 5 cc) 2 needles (adult: 22 gauge or preferably larger butterfly
or standard needle; pediatric: 25 or 23 gauge butterfly orstandard needle)
Gloves (sterile &nonsterile)
Tourniquet Sterile gauze pad Adhesive strip or tape Self-sticking patient labels Plastic zip lock specimen bagsDr.T.V.Rao MD 25
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. Barrier protection for the phlebotomist
consists of the latex gloves.
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Locate the vein
Prep kit Alcohol 5 sec. Dry 30-60 sec ( resource poor conditions )
Ideal to collect with alcohol swabs containing 2%Chlorhexidine and 70% isopropyl alcohol
Remove caps, clean with alcohol
Put on gloves
Without palpating, draw 20 ml and put 10 inanaerobic and 10 in aerobic bottle
Dispose of syringe in sharps container
Label bottles and send to lab
Obtaining Blood
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Method of Blood Collection
A minimum of 10 ml of blood istaken through venipunctureand injected into two or more"blood bottles" with specific
media for aerobic andanaerobic organisms.
The blood is collected usingclean technique. This requiresthat both the tops of the culturebottles and the venipuncturesite of the patient are cleanedprior to collection with alcoholswabs containing 2%Chlorhexidine and 70%isopropyl alcohol.
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The area of skin is cleaned with adisinfectant, or an alcohol swab.
Using sterile gloves, do notwipe away the surgicalsolution, touch the puncture
site, or in any waycompromise the sterileprocess. It is vital that theprocedure is performed in assterile a manner as possibleas the persistent presence ofskin commensals in bloodcultures could indicateendocarditis but they aremost often found ascontaminants
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The vein is anchored and the
needle is inserted.
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The vacutainer tube is depressed into
the needle to begin drawing blood
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Additional vacutainer tubes can be utilized. Determine what tests areordered and what tubes will be necessary BEFORE you begin to draw
blood, and determine the order of draw for the tubes..
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When the final tube is being drawn, release thetourniquet. Then remove the tube, and remove the
needle.
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After the needle is removed from the vein, apply firm
pressure over the site to achieve haemostasis.
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Apply a bandage to the area.
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Preparation of Cap before
Injecting BloodPrep the rubber
cap of the bloodculture bottleswith an alcoholpad in a circular
motion. Allowthe alcohol todry.
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Inject the Blood ..
Inject the bloodinto the Selected
MediaGently rotate the
bottles to mix the
blood & the broth(do not shakevigorously).
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Follow the universal precautions
when disposing NeedleDispose of
needle in
sharpscontainer anddispose of otherwaste in propercontainer
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Label the tubes, checking the requisition for the
proper identification.
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Patients name
Hospital number (Patient ID)
Patients location (room and bed #)
Date and time of collection
Collectors initials
Site of venipuncture
Or other information as per facility Include you Mobile Contact No A vital
information can be delivered any time
Give the all possible Medical
Information
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Document the Medical
Records
Document the
following in themedical record:
Date & timespecimen obtained
Site of specimencollection
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Frequency of Collection
Frequency of Collection
Depends if bacteremia is
transient, intermediate or
continuousNumber of cultures
collected are usually
inversely related to the
type of bacteremia
Usually x3 from
different body sites
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Second Set
If 2 or more sets ofblood cultures have
been ordered,obtain the secondset in the samemanner as the first,making a newvenipuncture at adifferent site.
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Most microbiological culture procedures
require the use of solid media, like blood
agar and Mac Conkeys agar plates that needto be visually monitored by trainedpersonnel at intervals of 24 hours. Theseconventional cultures using normal media
take at least a minimum of 72 hours to isolatethe pathogen and carry out susceptibility testto know the efficacy of antibiotics on simpleaerobic bacteria.
Traditional Methods in
Blood cultures
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Bacteria and Fungi Are Identifiedby Phenotypic Characters
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Biochemical Tests gives BetterClues in Identification
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Newer Blood Culture Methods
Newer Blood Culture Systems
Biphasic Broth-Slide System
Agar paddles attached to top of bottle
Closed system
Continuous Monitoring Blood Culture Systems
BacTecmeasures 14CO2
BacTec 9000 Seriesmeasures CO2
ESPmeasures consumption of gases
BacT-Alertmeasures change in pH
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Automation reduces the
time requirement But this can be completed
within 30 hours by
using automatedtechniques. This isespecially useful whenlarge number ofspecimens needs to becultured, as theinstrument, which hasbeen programmed for thesame, automaticallyscreens these.
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BacT/AlerT 3D culture
system BacT/AlerT 3D culture
system. This is the firstautomated non-
radiometric and non-invasive culture systemthat continuouslymonitors system forculture of bacteria (bothaerobic and anaerobic),
fungi and mycobacteria.All these bacteria can becultured using differentmedia as prescribed..
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bioMrieux
BacT/ALERT 3D The bioMrieux
BacT/ALERT 3Dprovides an optimal
environment for therecovery of a wide rangeof pathologicalorganisms, includingbacteria, yeasts and
mycobacteria; utilizingproprietary plastic culturebottles ensuring addedsafety to the user.
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BacT/ALERT 3D Microbial
Detection System This newest generation ofthe time-testedBacT/ALERT system offersadvantages in every
dimension of testing. Fromits space-saving modulardesign to its easy touch-screen operation andflexible data management
options, every laboratorywill find something to loveabout the BacT/ALERT 3D!
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P i i l f f ti i f B T
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Principles of functioning of BacTalert Monitors
Microorganisms multiply in themedia, generating CO2. As CO2increases, the sensor in thebottle turns a lighter colour.
Measuring reflected light, the
BacT/ALERT 3D monitors anddetects color changes in thesensor.
Algorithms analyze the data todetermine positivity, and thelaboratory is notified
immediately with visual andaudible alarms.
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Principles in BacT/AlerT 3Dculture system
This is a closed systemand works on thecolorimetric principle of
detection of CO2produced by theorganisms. The CO2causes a lowering of thepH of the medium, whichin turn produces a colour
change in a sensorattached to the CO2-sensitive base of eachbottle.
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Automation improves
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Automation improvesquality of services
Overall, laboratoriestransitioning fromconventional to
automated processesfind thattechnologists andmicrobiologists aremore open toinnovation andimproved quality.
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After inoculating the culture vials, they are
sent to the clinical pathology microbiologydepartment. Here the bottles are entered intoa blood culture machine, which incubate thespecimens at body temperature. The bloodculture instrument reports positive blood
cultures (cultures with bacteria present, thusindicating the patient is "bacteremia"). Mostcultures are monitored for 5 days after whichnegative vials are removed.
Automation Signals
Bacteremia cases
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A vial is positive, a microbiologist will perform a
Gram Stain on the blood for a rapid, general ID ofthe bacteria, which they will report to the attending
physician of the bacteremic patient. The blood is alsosubcultured onto agar plates to isolate thepathogenic organism for culture and susceptibilitytesting, which takes up to 3 days. This culture &
sensitivity (C&S) process identifies the species ofbacteria. Antibiotic sensitivities are then assessed onthe bacterial isolate to inform clinicians onappropriate antibiotics for treatment.
The positives cases to be
proceeded without delay
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Culturing Mycobacterium
from Blood Mycobacterial growth is
generally observed within aweek in case of smear (1+)
positive. Speciation into
mycobacterium tuberculosiscomplex and mycobacteriaother than tuberculosis takesan additional three days.
An important Investigationin AIDS and otherImmunosuppressed patients
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Testing drug resistance in
Tuberculosis a priority Susceptibility testing to
primary line of anti-tuberculosis drugs viz
streptomycin, isoniazid,rifampicin, ethambutoland pyrizinamide andsecondary line of drugsviz kanamycin, para-
amino salicylic acid,cycloserine, ethionamide,capreomycin etc requires5-10 days.
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Rapid Susceptibility Testing
Rapid susceptibility willbe carried out for gramnegative and
staphylococcal isolatesand other isolates onrequest. These will bereported within 12 hoursusing API systems.
Automation has made iteasier to arrive at aprecise laboratorydiagnosis of infection
Th C t i t d
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If the skin is not adequately cleansed before
drawing blood for culture, bacteria on the skinwill be injected into the bottle, producing a falsepositive blood culture
It is difficult for the physician to determinewhether the bacteria growing in the blood cultureis a real pathogen causing bloodstream infection
or whether bacteria on the skin have contaminatedthe culture. This can lead to excess use ofantibiotics and prolongation of hospital stay.
The Contaminated
Blood Culture
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The programme created by
Dr.T.V.Rao MD as TechnicalSeries for Microbiologists in theDeveloping World
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