Blood culturing in infectious diseases - PowerPoint PPT Presentation

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Blood culturing in infectious diseases


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Title: Blood culturing in infectious diseases

  • Dr.T.V.Rao MD

What is a Blood Culture?
  • A blood culture is a laboratory test in which
    blood is injected into bottles with culture media
    to determine whether microorganisms have invaded
    the patients bloodstream.

Need for Blood Culture?
  • No microbiological test is more essential to the
    clinician than the blood culture. The finding of
    pathogenic microorganisms in a patients
    bloodstream is of great importance in terms of
    diagnosis, prognosis, and therapy.
  • - L. Barth Reller, Clin. Infect. Diseases,

Blood Culture is done to Detect Infectious
  • Blood culture is a microbiological culture of
    blood. It is employed to detect infections that
    are spreading through the bloodstream (such as
    bacteremia, septicemia amongst others). This is
    possible because the bloodstream is usually a
    sterile environment

Proof in Blood borne Infection
  • A clinically suspected infection is ultimately
    confirmed by isolation or detection of the
    infectious agent. Subsequent identification of
    the microorganism and antibiotic susceptibility
    tests further guide effective antimicrobial
    therapy. Bloodstream infection is the most severe
    form of infection and is frequently
    life-threatening, and blood culture to detect
    circulating microorganisms has been the
    diagnostic standard.

  • Bacteremia presence of bacteria in blood stream
  • Some conditions have a period of bacteremia as
    part of the disease process (ex. Meningitis,
  • Septicemia bacteremia plus clinical signs and
    symptoms of bacterial invasion and toxin

(No Transcript)
Definitions (contd)
  • Primary Bacteremia blood stream bacterial
    invasion with no preceding or simultaneous site
    of infection with the same microorganism
  • Secondary Bacteremia isolation of a
    microorganism from blood as well as other site(s)

Bacteremia and Fungemia Episodes
  • Transient
  • Comes and goes
  • Usually occurs after a procedural manipulation
    (ex. Dental procedures)
  • Intermittent
  • Can occur from abscesses at some body site that
    is seeding the blood
  • Continuous Bacteremia

Bacteremia Complications
  • Warm shock fever, increased pulse,
    hyperventilation, and warm, dry flushed skin
  • Cold shock decreased blood pressure, increased
    pulse, and rapid, shallow respirations
  • Septic chock
  • Hemodynamic changes, decreased tissue perfusion
    and compromised organ tissue function
  • Mortality 40 to 50

Bacteremia/Septicemia Risk Factors
  • Immunocompromised patients
  • Increased use of invasive procedures
  • Age of patient
  • Administration of drug therapy

Sources of Bacteremia Spread
  • Pericarditis and Peritonitis
  • Pneumonias
  • Pressure sores
  • Prosthetic medical devices
  • Total hip replacement
  • Skeletal system
  • Skin and soft tissue

Blood culturing most important and life saving
  • Needs optimal Methods for Diagnosis of Blood
    Borne Pathogens

Blood Collection
  • Aseptic collection procedure is critical Amount
    of blood
  • 110 ratio of blood to broth
  • Younger than 10 years 1 ml of blood for every
    year of life
  • Over 10 years 20 ml

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

Blood Culture Methods
  • Conventional Broth Systems
  • One aerobic bottle and one anaerobic bottle per
    blood collection
  • Aerobic broth contains soybean casein digest
    broth, Tryptic or trypticase soy broth, Brucella
    agar or Columbia broth base
  • Anaerobic broth is usually the same as aerobic
    with addition of 0.5 cysteine in an aerobic
  • Must be subcultured and gram stained manually

  • Venipuncture is the process of obtaining
    intravenous access for the purpose of intravenous
    therapy or obtaining a sample of venous blood.
    This procedure is performed by medical laboratory
    scientists, 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 two reasons, to obtain blood for diagnostic
    purposes or to monitor levels of blood components
    (Lavery Ingram 2005).

Phlebotomy Definition
  • phlebotomy (fli) noun the act or practice of
    bloodletting as a therapeutic measure
  • Phlebotomy from Greek words, phlebo, relates to
    veins, tomy, relates to cutting.
  • Opening a vein to collect blood

  • Properly labelled sample is essential so that the
    results of the test match the patient. The key
    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.

Principles for Collection
  • Gloves will be worn in accordance with standard
  • Appropriate verification of the patient's
    identity, by means of an armband or area specific
    procedure, will occur before the specimen
  • Cultures should be drawn before administration
    of antibiotics, if possible. ???
  • blood cultures should be drawn from lines, but
    should be drawn viavenipuncture.

What Materials We need
  • 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 or standard needle)
  • Gloves (sterile nonsterile)
  • Tourniquet
  • Sterile gauze pad
  • Adhesive strip or tape
  • Self-sticking patient labels
  • Plastic zip lock specimen bags

The requisitions form should be completely filled
out, and the requisition must indicate the tests
Self Protection
A few ways to make sure your role in the
collection process is carried out with
efficiency, orderliness and safety
Steps 1 3, Check, Explain, Wash
  • 1.Identify the patient
  • 2.Explain the procedure to the patient.
  • 3.Wash hands with soap and water with friction
    for 15 seconds or use alcohol based hand rub

  • 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 or standard needle)
  • Gloves (sterile nonsterile)
  • Tourniquet
  • Sterile gauze pad
  • Adhesive strip or tape
  • Self-sticking patient labels
  • Plastic zip lock specimen bags

. Barrier protection for the phlebotomist
consists of the latex gloves.
Obtaining Blood
  • 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 in
    anaerobic and 10 in aerobic bottle
  • Dispose of syringe in sharps container
  • Label bottles and send to lab

Method of Blood Collection
  • A minimum of 10 ml of blood is taken through
    venipuncture and injected into two or more "blood
    bottles" with specific media for aerobic and
    anaerobic organisms.
  • The blood is collected using clean technique.
    This requires that both the tops of the culture
    bottles and the venipuncture site of the patient
    are cleaned prior to collection with alcohol
    swabs containing 2 Chlorhexidine and 70
    isopropyl alcohol.

The area of skin is cleaned with a disinfectant,
or an alcohol swab.
  • Using sterile gloves, do not wipe away the
    surgical solution, touch the puncture site, or in
    any way compromise the sterile process. It is
    vital that the procedure is performed in as
    sterile a manner as possible as the persistent
    presence of skin commensals in blood cultures
    could indicate endocarditis but they are most
    often found as contaminants

The vein is anchored and the needle is inserted.
The vacutainer tube is depressed into the needle
to begin drawing blood
Additional vacutainer tubes can be utilized.
Determine what tests are ordered and what tubes
will be necessary BEFORE you begin to draw blood,
and determine the order of draw for the tubes. .
When the final tube is being drawn, release the
tourniquet. Then remove the tube, and remove the
After the needle is removed from the vein, apply
firm pressure over the site to achieve
Apply a bandage to the area.
Preparation of Cap before Injecting Blood
  • Prep the rubber cap of the blood culture bottles
    with an alcohol pad in a circular motion. Allow
    the alcohol to dry.

Inject the Blood ..
  • Inject the blood into the Selected Media
  • Gently rotate the bottles to mix the blood the
    broth (do not shake vigorously).

Follow the universal precautions when disposing
  • Dispose of needle in sharps container and dispose
    of other waste in proper container

Label the tubes, checking the requisition for the
proper identification.
Give the all possible Medical Information
  • 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

Document the Medical Records
  • Document the following in the medical record
  • Date time specimen obtained
  • Site of specimen collection

Frequency of 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

Second Set
  • If 2 or more sets of blood cultures have been
    ordered, obtain the second set in the same manner
    as the first, making a new venipuncture at a
    different site.

Traditional Methods in Blood cultures
  • Most microbiological culture procedures require
    the use of solid media, like blood agar and Mac
    Conkeys agar plates that need to be visually
    monitored by trained personnel at intervals of 24
    hours. These conventional cultures using normal
    media take at least a minimum of 72 hours to
    isolate the pathogen and carry out susceptibility
    test to know the efficacy of antibiotics on
    simple aerobic bacteria.

Bacteria and Fungi Are Identified by Phenotypic
Biochemical Tests gives Better Clues in
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
  • BacTec measures 14CO2
  • BacTec 9000 Series measures CO2
  • ESP measures consumption of gases
  • BacT-Alert measures change in pH

Automation reduces the time requirement
  • But this can be completed within 30 hours by
    using automated techniques. This is especially
    useful when large number of specimens needs to be
    cultured, as the instrument, which has been
    programmed for the same, automatically screens

BacT/AlerT 3D culture system
  • BacT/AlerT 3D culture system. This is the first
    automated non-radiometric and non-invasive
    culture system that continuously monitors system
    for culture of bacteria (both aerobic and
    anaerobic), fungi and mycobacteria. All these
    bacteria can be cultured using different media as

bioMérieux BacT/ALERT 3D
  • The bioMérieux BacT/ALERT 3D provides an optimal
    environment for the recovery of a wide range of
    pathological organisms, including bacteria,
    yeasts and mycobacteria utilizing proprietary
    plastic culture bottles ensuring added safety to
    the user.

BacT/ALERT 3D Microbial Detection System
  • This newest generation of the time-tested
    BacT/ALERT system offers advantages in every
    dimension of testing. From its space-saving
    modular design to its easy touch-screen operation
    and flexible data management options, every
    laboratory will find something to love about the
    BacT/ALERT 3D!

Principles of functioning of BacT alert Monitors
  • Microorganisms multiply in the media, generating
    CO2. As CO2 increases, the sensor in the bottle
    turns a lighter colour.
  • Measuring reflected light, the BacT/ALERT 3D
    monitors and detects color changes in the sensor.
  • Algorithms analyze the data to determine
    positivity, and the laboratory is notified
    immediately with visual and audible alarms.

Principles in BacT/AlerT 3D culture system
  • This is a closed system and works on the
    colorimetric principle of detection of CO2
    produced by the organisms. The CO2 causes a
    lowering of the pH of the medium, which in turn
    produces a colour change in a sensor attached to
    the CO2-sensitive base of each bottle.

Automation improves quality of services
  • Overall, laboratories transitioning from
    conventional to automated processes find that
    technologists and microbiologists are more open
    to innovation and improved quality.

Automation Signals Bacteremia cases
  • After inoculating the culture vials, they are
    sent to the clinical pathology microbiology
    department. Here the bottles are entered into a
    blood culture machine, which incubate the
    specimens at body temperature. The blood culture
    instrument reports positive blood cultures
    (cultures with bacteria present, thus indicating
    the patient is "bacteremia"). Most cultures are
    monitored for 5 days after which negative vials
    are removed.

The positives cases to be proceeded without delay
  • A vial is positive, a microbiologist will perform
    a Gram Stain on the blood for a rapid, general ID
    of the bacteria, which they will report to the
    attending physician of the bacteremic patient.
    The blood is also subcultured onto agar plates
    to isolate the pathogenic organism for culture
    and susceptibility testing, which takes up to 3
    days. This culture sensitivity (CS) process
    identifies the species of bacteria. Antibiotic
    sensitivities are then assessed on the bacterial
    isolate to inform clinicians on appropriate
    antibiotics for treatment.

Culturing Mycobacterium from Blood
  • Mycobacterial growth is generally observed within
    a week in case of smear (1) positive.
  • Speciation into mycobacterium tuberculosis
    complex and mycobacteria other than tuberculosis
    takes an additional three days.
  • An important Investigation in AIDS and other
    Immunosuppressed patients

Testing drug resistance in Tuberculosis a priority
  • Susceptibility testing to primary line of
    anti-tuberculosis drugs viz streptomycin,
    isoniazid, rifampicin, ethambutol and
    pyrizinamide and secondary line of drugs viz
    kanamycin, para-amino salicylic acid,
    cycloserine, ethionamide, capreomycin etc
    requires 5-10 days.

Rapid Susceptibility Testing
  • Rapid susceptibility will be carried out for gram
    negative and staphylococcal isolates and other
    isolates on request. These will be reported
    within 12 hours using API systems. Automation has
    made it easier to arrive at a precise laboratory
    diagnosis of infection 

The Contaminated Blood Culture
  • If the skin is not adequately cleansed before
    drawing blood for culture, bacteria on the skin
    will be injected into the bottle, producing a
    false positive blood culture
  • It is difficult for the physician to determine
    whether the bacteria growing in the blood culture
    is a real pathogen causing bloodstream infection
    or whether bacteria on the skin have contaminated
    the culture. This can lead to excess use of
    antibiotics and prolongation of hospital stay.

  • The programme created by Dr.T.V.Rao MD as
    Technical Series for Microbiologists in the
    Developing World
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