Microorganisms

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Microorganisms show-up every once in a while. It is essential to know 'em.

Microorganisms

Fungi

Name (disease) Kingdom Size Shape Stains Other (microscopic) Clinical References Image
Aspergillus (aspergillosis) Fungi  ? Hyphae that branching
with 45 degrees angle
PAS-D Fruiting heads when aerobic  ? Immunosuppression [1]
Aspergillus. (WC)
Zygomycota (zygomycosis);
more specific
Mucorales (mucormycosis)
Fungi  ? Branching hyphae with variable width  ? Granulomata assoc. Diabetes, immunodeficient [1]
Zygomycosis. (WC)
Coccidioides, usually C. immitis
(coccidioidomycosis)
Fungi Large - 20-60 micrometers,
endospores 1-5 micrometers
Spherules Stains? Other? Immunodeficient [1] Coccidioidomycosis (med.sc.edu)
C. immitis (WC)
Histoplasma (histoplasmosis) Fungi 2-5 micrometers Spherical GMS Intracellular (unlike candida), granulomata Source: soil with bird droppings [1]
Histoplasmosis. (WC)
Blastomyces (blastomycosis) Fungi 5-15 micrometres Spherical (yeast) Stains? Granulomas, broad-based budding yeast Habitat: Northeast America, Africa [1][2]
Blastomyces. (WC)
Paracoccidioides (paracoccidioidomycosis) Fungi 6-60 micrometres Spherical (yeast) Stains? Multiple budding "steering wheel" appearance Clinical??? [1]
P. brasiliensis (WC)
Pneumocystis jirovecii (pneumocystis carinii pneumonia; abbrev. PCP) Fungi (previously thought to be a protozoan) 7-8 micrometres "Dented ping-pong ball" GMS Usually in clusters of alveolar casts with a honeycomb appearance HIV/AIDS associated [3]
PCP. (WC)
Cryptococcus (cryptococcosis) Fungi 5-15 micrometres Yeast GMS Prominent (i.e. thick polysaccharide) capsule HIV/AIDS associated, most common CNS fungus [1]
Crytococcosis - mucicarmine (WC)

Notes:

  • Bold text = key features.

Fungi

  • There are lots of 'em. Below are a few of 'em.

Terminology:[4]

  • Hyphae = microscopic filamentous growth (of fungi) -- single cell.
  • Mycelial = filamentous network of hyphae.
  • Septae/septation = hyphae may be subdivided by septae -- if they aren't they are one mass of protoplasm. (?)
  • Dimorphism = exist in two forms; e.g. single cell (yeast) and mycelial growth.
  • Pseudohyphae = looks like hyphae --but branching pattern is created by separate cells.[5]

Tissue invasive fungi

Typically:[6]

  • Mucor.
  • Aspergillus.

List

Worms & stuff

Schistosomiasis

See Urine cytopathology.

General

  • Trematode, i.e. type of worm.

Microscopic

Features of ova (S. haematobium):[7]

  • Elliptical ~140 micrometres max dimension.
  • "Spike" approx. the size of a PMN.

Images

www:

Toxoplasma

General

  • Common CNS infection.
    • Toxoplasma gondii - pathogenic; causes toxoplasmosis.
  • Protozoa.
  • A TORCH infection.

Microscopic

General:

  • Dependent on location in body.

Lymph node

LN features:[8]

  • Reactive germinal centers (pale areas - larger than usual).
    • Often poorly demarcated - due to loose epithelioid cell clusters at germinal center edge - key feature.
  • Epithelioid cells - perifollicular & intrafollicular.
    • Loose aggregates of histiocytes (do not form round granulomas):
      • Abundant pale cytoplasm.
      • Nucleoli.
  • Monocytoid cells (monocyte-like cells) - in cortex & paracortex.
    • Large cells in islands/sheets key feature with:
      • Abundant pale cytoplasm - important.
      • Well-defined cell border - important.
      • Singular nucleus.
    • Cell clusters usually have interspersed neutrophils.

Images (lymph node):

CNS

CNS features:[9]

  • Granular appearing ball ~ 2x the size of resting lymphocyte.
Images (CNS)

www:

Heart

Features:

  • Intramuscular organisms.

DDx:

Images (heart):

IHC

  • IHC for toxoplasma.[10]

Strongyloidiasis

General

  • Causes by worm Strongyloides stercoralis.
  • High case mortality rate ~ 70%.[11]
  • May present after years of latency due to immune suppression.[12]

Location:

  • Lung. (???)

Microscopic

Features:

  • Long worms.
  • ~10-15 micrometers wide.

Images

www:

Echinococcus

Microscopic

Features:

  • Laminated wall +/- calcification.[13]
  • Organisms:
    • Hooklets.
    • Scoleces - knoblike anterior end of a tapeworm.[14]

Enterobius vermicularis

  • AKA pinworm.

General

Gross

  • Peri-anal white squiggly thing ~ 2-13 mm in length.

Image:

Microscopic

Features - organism:

  • 0.2-0.5 mm width x 2-13 mm length.
  • Characteristic triangular "spikes" seen on cross section - base x height ~ 30 x 30 μm.
    • Spikes is in quotations, as these are really a longitudinal blade-like ridges, that run the length of the worm.

Features - eggs:[16]

  • Ovoid - double walled shells, one side flat.

Images

www:

Trichinella

General

  • Causes Trichinosis.
    • Classically associated with uncooked pork.[17]
  • Several types; most due to T. spiralis.[17]

Microscopic

Features:

  • Worm.

Image:

Cysticercosis

General

  • Caused by Taenia solium; pork tapeworm.
  • May cause epilepsy; most common parasitic CNS infection.[19]

Gross

  • Multiple cystic spaces.

Image:

Microscopic

Features:

  • Large ovoid body with complex structures (cross-section of worm) - size: millimetres.
    • +/-External eosinophilic microvilli.
    • +/-Gastrointestinal tract - ovoid structure within the worm.

Notes:

  • Histomorphology is not distinctive for the type... microbiology usually figures it out.

Images:

Rhinosporidiosis

Not to be confused with rhinoscleroma.

General

  • Caused by parasite Rinosporidium seeberi.
    • India, Sri Lanka.
  • Nasal mass.
    • May present with obstruction.[20]

Microscopic

Features:[21][20]

  • Globular cysts ~ 100 micrometers with endospores:
    • Hyperchromatic (blue) spherical 10-100 micrometer.

Images:

Stains

Leishmaniasis

General

  • Caused by protozoa in the group Leishmania group.
  • Transmitted to humans by the sand fly.

May be:

Microscopic

Features:

  • Small ~1-2 micrometers.

Images

www:

Stains

Viruses

This is a fairly big topic. There are about half a dozen viral inclusions (e.g. CMV, HSV, VZV, adenovirus) a decent pathologist ought to be able to identify. The virus article covers 'em.

Bacteria

This is a small topic when considered from the perspective of an anatomical pathologist. Most stuff is sorted-out by microbiology.

Microorganisms and cancer

Viruses and cancer

A number of microorganisms are associated with the development of cancer:[25]

Bacteria and cancer

Parasites and cancer

See also

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 682. ISBN 978-1416025887.
  2. http://pathmicro.med.sc.edu/mycology/mycology-6.htm
  3. Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 684. ISBN 978-1416025887.
  4. http://www.fungionline.org.uk/1intro/3growth_forms.html
  5. http://pathmicro.med.sc.edu/mycology/mycology-3.htm
  6. CM 17 Apr 2009.
  7. URL: http://path.upmc.edu/cases/case622/dx.html. Accessed on: 26 January 2012.
  8. Ioachim, Harry L; Medeiros, L. Jeffrey (2008). Ioachim's Lymph Node Pathology (4th ed.). Lippincott Williams & Wilkins. pp. 113. ISBN 978-0781775960.
  9. URL: http://moon.ouhsc.edu/kfung/jty1/opaq/PathQuiz/N0I001-PQ01-M.htm. Accessed on: 19 October 2010.
  10. URL: http://moon.ouhsc.edu/kfung/jty1/opaq/PathQuiz/N0I001-PQ01-M.htm. Accessed on: 19 October 2010.
  11. Lim, S.; Katz, K.; Krajden, S.; Fuksa, M.; Keystone, JS.; Kain, KC. (Aug 2004). "Complicated and fatal Strongyloides infection in Canadians: risk factors, diagnosis and management.". CMAJ 171 (5): 479-84. doi:10.1503/cmaj.1031698. PMID 15337730.
  12. Siddiqui, AA.; Berk, SL. (Oct 2001). "Diagnosis of Strongyloides stercoralis infection.". Clin Infect Dis 33 (7): 1040-7. doi:10.1086/322707. PMID 11528578.
  13. Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 448. ISBN 978-1416054542.
  14. http://www.thefreedictionary.com/scoleces. Accessed on: 10 January 2010.
  15. Dahlstrom, JE.; Macarthur, EB. (Oct 1994). "Enterobius vermicularis: a possible cause of symptoms resembling appendicitis.". Aust N Z J Surg 64 (10): 692-4. PMID 7945067.
  16. Lefkowitch, Jay H. (2006). Anatomic Pathology Board Review (1st ed.). Saunders. pp. 685. ISBN 978-1416025887.
  17. 17.0 17.1 Kaewpitoon N, Kaewpitoon SJ, Philasri C, et al. (October 2006). "Trichinosis: epidemiology in Thailand". World J. Gastroenterol. 12 (40): 6440–5. PMID 17072975. http://www.wjgnet.com/1007-9327/12/6440.asp.
  18. URL: http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/msfrm.html. Accessed on: 5 December 2010.
  19. Prasad KN, Prasad A, Verma A, Singh AK (November 2008). "Human cysticercosis and Indian scenario: a review". J. Biosci. 33 (4): 571–82. PMID 19208982.
  20. 20.0 20.1 20.2 Morelli, L.; Polce, M.; Piscioli, F.; Del Nonno, F.; Covello, R.; Brenna, A.; Cione, A.; Licci, S. (2006). "Human nasal rhinosporidiosis: an Italian case report.". Diagn Pathol 1: 25. doi:10.1186/1746-1596-1-25. PMC 1560165. PMID 16945122. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1560165/.
  21. URL: http://www.histopathology-india.net/Rhino.htm. Accessed on: 4 January 2012.
  22. URL: http://www.arquivosdeorl.org.br/conteudo/acervo_eng.asp?id=428. 4 January 2012.
  23. 23.0 23.1 Goto, H.; Lindoso, JA. (Apr 2010). "Current diagnosis and treatment of cutaneous and mucocutaneous leishmaniasis.". Expert Rev Anti Infect Ther 8 (4): 419-33. doi:10.1586/eri.10.19. PMID 20377337.
  24. den Boer, ML.; Alvar, J.; Davidson, RN.; Ritmeijer, K.; Balasegaram, M. (Sep 2009). "Developments in the treatment of visceral leishmaniasis.". Expert Opin Emerg Drugs 14 (3): 395-410. doi:10.1517/14728210903153862. PMID 19708817.
  25. Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 168. ISBN 978-1416054542.

External links