MLAB 2434

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MLAB 2434 CLINICAL MICROBIOLOGYSUMMER,
2005CECILE SANDERS KERI BROPHY

• Chapter 7 General Concepts in Specimen
  Collection and Handling

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Basic Principles of Specimen Collection
• Specimen should be taken in acute phase of
  infection AND before antibiotics are administered
• Written order must specify site of culture
  (example wound on left arm)

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Avoid normal flora and colonizing organisms
• Compare test results with suspected diagnosis

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Appropriate Collection Techniques
• Aspirates and tissues
• Aspirates and tissues present few problems, if
  collected using sterile technique
• Lesions, wounds and abscesses cultures should be
  from as deep in the wound as possible

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Swabs
• Used only as a last resort
• Steps
• Clean wound
• Explore wound
• Obtain fresh and quality culture material
• Should be placed in a holding medium to protect
  pathogens without permitting multiplication
  during transport

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Patient Education and Preparation
• If patient is responsible for collecting
  specimen, good instructions are critical
• Urine midstream clean catch first morning
  specimen
• Sputum collect sputum NOT spit
• Stools usually 3 vials and at least 4 days
  after barium Xrays

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Preservation, Storage, and Transport of Specimens
• Concerns
• Overgrowth
• Death of microorganisms
• Inaccurate quantitation
• Loss of organisms from drying
• Protection from oxygen
• Protection from clotting
• Safety of transporter

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Preservatives
• Urine boric acid
• Stool phosphate-buffered saline (PBS)
• Anticoagulants
• Needed in any specimen that might clot (blood,
  serum, joint fluids)
• Sodium polyanethol sulfonate (SPS)

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Use of Holding and Transport Media
• Swabs placed in Modified Stuart transport medium
  or Cary-Blair transport medium
• Blood placed in broth culture medium
• Unprotected specimens
• Sputums, body fluids, tissues, catheters, medical
  devices, and specimens for sterility culture
• Should be processed ASAP

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Storage of Specimens
• Urine, viral blood specimens, catheters and swabs
  should be refrigerated
• Blood and CSF should be processed ASAP
• Specimens for fungus cultures can be kept at room
  temperature
• Respiratory and stool cultures should be
  processed ASAP if at all possible, but
  refrigerated if immediate processing is not
  possible

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Mailing Specimens
• Regulated by U.S. Dept. of Health and Human
  Services
• Primary container must be securely closed,
  watertight
• Secondary container has sufficient absorbent
  material to absorb contents in case of breakage
• Final container is an approved mailing container
  with biohazard symbol and contact phone number
  for CDC
• Page 244 in textbook

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Safety
• Universal Precautions
• Specimen processing should be conducted in a
  Class II safety cabinet (hood)
• Labeling and Rejection of Specimens
• Requisitions must include source, diagnosis or
  history, and test(s) requested

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Unacceptable Specimens
• Labels on requisition and on specimen must match
• Noninvasive vs. invasive specimens
• Rejected specimens
• Leaking
• Syringes with needles attached
• Stools contaminated with urine or barium
• Anaerobic cultures on inappropriate sources
• Unpreserved specimens over 2 hours old

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Refrigerated blood cultures
• Dried-up specimens
• Specimens in formalin
• Processing of Clinical Samples for Optimal
  Organism Recovery
• Prioritization (Table 7-2, p. 247)
• Level 1- Critical/invasive
• Level 2 Unpreserved
• Level 3 Accuracy of quantitation affected
• Level 4 Protected/Preserved

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Gross Examination of Specimens check specimen
  and requisition
• Direct Examination Techniques
• Direct Microscopic Examination (Table 7-3, p.
  250, text)
• Determine quality of specimen
• Diagnose infectious disease
• Guide routine culture interpretation
• Dictate the need for nonroutine processing

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Smear Preparation
• Tissues
• Swabs
• Aspirates and body fluids
• Single drop smear
• Centrifuged sediment smear
• Layered smear
• Cytocentrifuged smear
• Additives

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Chapter 7- General Concepts in Specimen
Collection and Handling (contd)

• Direct Smears NOT useful
• Throats, nasopharyngeal swabs
• Urine
• Female genital tract
• Primary Inoculation of Routine Specimens
• Types of Culture Media
• Nonselective vs. Selective
• Differential
• Enriched
• Broths