Identification of Organisms

A wide range of microorganisms, from bacteria to viruses, can be identified in formalin-fixed, paraffin embedded-tissue sections. In many cases, immunohistochemistry offers distinct advantages over special stains, both in terms of overall sensitivity as well as the ability to detect the presence of antigen even when the organism is no longer intact. In some cases, in situ hybridization is the best method of detecting the presence of a viral organism. Below is a gallery of images of organisms identified by immunohistochemistry or in situ hybridization.

Organisms that can be identified by Immunohistochemistry/In situ Hybridization:

Adenovirus
Chlamydia
Cytomegalovirus
Epstein-Barr Virus (EBER1 by in situ hybridization)
Epstein-Barr Virus (EBV-LMP by immunohistochemistry)
Helicobacter pylori
Hepatitis B core and surface antigens
Herpes simplex (HSV-I/II)
HHV-8 (KSHV)
JC virus (SV-40)
Legionella
Parvovirus
Pneumocystis carinii
Respiratory syncytial virus (RSV)
Toxoplasma gondii
Varicella/zoster


Toxoplasma This brain biopsy from a patient with rapid onset of symptoms suggested the presence of toxoplasma, which was confirmed using immunohistochemical studies in which toxoplasma tachyzoites are identified.	HBsAg Antibodies to Hepatitis B Surface antigen (HBsAg) show localization of the antigen in the cytoplasm of the infected hepatocytes in a characteristic granular staining pattern.

Helicobacter pylori A gastric biopsy from a patient with gastritis demonstrates numerous Helicobacter pylori organisms by immunohistochemistry.	HHV-8 The speckled nuclear pattern of HHV- 8 immunoreactivity confirms the diagnosis of Kaposi's sarcoma in an AIDS patient.

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