Mycobacteriaceae

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Mycobacteriaceae Part IVMicroscopic Examination

• Created by Michele L. Jurgensmeier MT(ASCP)
• Edited by Kathy Talmon MT(ASCP)SM
• Voice over lecturer Carol Larson MSEd, MT(ASCP)
• Clinical Laboratory Science Program

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Microscopic Examination

• Direct specimen detection important due to slow
  growth rate of organisms
• Purposes
• Determine acid fast characteristic
• Detect new cases
• Monitor progress of disease / treatment
• Criteria for patient release from hospital

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Microscopic Examination

• Fluorochrome stains (Auramine O)
• Primary stain fluorescent dyes
• Counter stain potassium permanganate
• AFB fluoresce yellow/gold against a black
  background

Enlarged view
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Microscopic Examination

• Fluorochrome stains (Auramine O)
• Screening procedure
• Advantages
• More sensitive than carbolfuchsin stains
• Examine on lower magnification
• View more fields in shorter time
• Disadvantages
• Rapidly growing mycobacteria do not stain
• Less specific

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Microscopic Examination

• Carbolfuschin stains (Ziehl-Neelsen / Kinyoun)
• Primary stain carbolfuschin
• Counter stain methylene blue
• AFB appear red and background material blue

Photo courtesy of CDC public image library
Content provider Dr. George P. Kubica
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Microscopic Examination

• Carbolfuschin stains (Ziehl-Neelsen / Kinyoun)
• Advantages
• More specific than fluorescent stains
• Stains all mycobacteria
• Disadvantages
• Longer examination time
• Less sensitive

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Microscopic Examination

• Interpretation of smears
• Examine 300 oil immersion fields
• Observe slides for morphology consistent with
  mycobacteria
• Other organisms may stain partially acid fast
• Quantify organisms
• Follow disease state

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Microscopic Examination Correlation With Culture
Results

• Extensive disease
• Good correlation
• Minimal or less-advanced disease
• Less correlation
• Antibiotic treatment
• Unsatisfactory laboratory procedures

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References

1. Mahon, C.R. Manuselis, G., Textbook of
   Diagnostic Microbiology, 2nd Ed., W.B. Saunders,
   2000
2. Forbes, B.A., Sahm, D. F., Weissfeld, A.S.,
   Bailey and Scotts Diagnostic Microbiology, 11th
   Ed., Mosby, 2002.
3. Koneman, Color Atlas and Textbook of Diagnostic
   Microbiology, 5th Ed., J.B. Lippincott Co., 1997
4. Murray PK, et al., Manual of Clinical
   Microbiology, 7th ed., ASM Publishing, Washington
   DC, 1999.