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Traditionally, staining of fungi and other microorganisms has been focused on hematoxylin, eosin and special staining techniques, and certain special stains are considered classics. Periodic Acid Schiff (PAS) and Grocott's Methenamine Silver (GMS) (for fungi and pneumocystis), the Steiner method (for spirochetes and Helicobacter pylori) and Mayer's or the Southgates's Mucicarmine method (for Cryptococcus) are a few techniques that provide beautiful details of many microorganisms.
Special stains, in conjunction with molecular diagnostics assays, continue to be useful diagnostic tools for identifying fungi and microorganisms. GMS provides details of kinetoplasts in pneumocystis, Bodian reveals the basement membrane of toxoplasmosis, and PAS lights up with a green tint to demonstrate the perinuclear details of histoplasmosis.
Immunohistochemistry (IHC) assays give permanent results of many microorganisms and infectious diseases for clinical and research applications. IHC assays and polymerase chain reaction gel assays are also useful to diagnose herpes simplex, varicella, enterovirus and HPV. HPV gels can demonstrate complete typing with the help of restriction enzymes.
At the same time, healthcare has seen increasing demand for decreasing hospital stays, improved patient care and rapid turnaround time. Automation has contributed to continuous workflow and more consistent results. And faster molecular diagnostic techniques are identifying diseases such as cytomegalovirus (a member of the herpes virus family), HPV and BK viruses. Even culture media in microbiology laboratories is racing to keep up, with faster growth of some microorganisms-48 hours or less. Since fungi are a large and diversified group, their identification usually depends upon culture appearance and microscopic morphology.
Molecular assays will continue to probe into the genetic realm of microorganism composition and provide faster, more in-depth answers to steer treatment of infectious and fungal diseases and microorganisms. Special stains will play a role in documenting the entities of fungi and microorganisms and may even become an adjunct test to confirm classification. As the trend moves toward molecular assays, telepathology will offer increased visibility, flexible consultations and rapid diagnosis in stat cases when needed.
M. Lamar Jones is anatomic manager, Department of Pathology, Wake Forest University Baptist Medical Center, Winston-Salem NC, and program director, School of Histotechnology, Davidson County Community College, Lexington, NC.
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