Blood culturing in infectious diseases

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BLOOD CULTURINGIN INFECTIOUS DISEASES

• Dr.T.V.Rao MD

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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.

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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,
  1996

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Blood Culture is done to Detect Infectious
Diseases

• 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

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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.

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Definitions

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

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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)

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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

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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

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Bacteremia/Septicemia Risk Factors

• Immunocompromised 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 medical devices
• Total hip replacement
• Skeletal system
• Skin and soft tissue

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Blood culturing most important and life saving
Investigation

• Needs optimal Methods for Diagnosis of Blood
  Borne Pathogens

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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

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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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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
  environment
• Must be subcultured and gram stained manually

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Venipuncture

• 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).

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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

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LABELING THE SAMPLE

• 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.

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Principles for Collection

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

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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

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The requisitions form should be completely filled
out, and the requisition must indicate the tests
ordered.
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Self Protection
A few ways to make sure your role 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 the procedure to the patient.
• 3.Wash hands with soap and water with friction
  for 15 seconds or use alcohol based hand 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 or standard needle)
• Gloves (sterile nonsterile)
• Tourniquet
• Sterile gauze pad
• Adhesive strip or tape
• Self-sticking patient labels
• Plastic zip lock specimen bags

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. Barrier protection for the phlebotomist
consists of the latex gloves.
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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

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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.

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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

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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 are ordered 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 the
tourniquet. 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 Blood

• Prep the rubber cap of the blood culture bottles
  with an alcohol pad in a circular motion. Allow
  the alcohol to dry.

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Inject the Blood ..

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

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Follow the universal precautions when disposing
Needle

• Dispose of needle in sharps container and dispose
  of other waste in proper container

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Label the tubes, checking the requisition for the
proper identification.
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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

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Document the Medical Records

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

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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

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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.

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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.

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

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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
  these.

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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
  prescribed..

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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.

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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!

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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 

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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.

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