Different body secretions, such as saliva, urine, throat washing, blood, CSF, cervical secretions, and bronchoalveolar lavage fluid, and tissue bits are the specimens that can be used for the culture.
Direct immunofluorescence test using specific fluorescein-labeled monoclonal antibodies has been used to detect CMV pp65 and pp67 proteins of the virus directly in the clini-cal specimens, such as blood leukocytes. These proteins are typically expressed only during replication of the virus in the tissues.
Cell culture is the definitive method for establishing diagno-sis of CMV infection. Body fluids or organ tissues are usually cultured on human diploid fibroblast cell lines and are incu-bated for development of the characteristic CPEs for at least 4–6 weeks.
Shell vial assay: Though cell culture is highly sensitive, buttakes a longer time of 4–6 weeks for identification of virus. To avoid that, shell vial assay is carried out for rapid detection of viruses. This is an adaptation of tissue culture, which pro-vides result more rapidly. In this method, the clinical speci-men is added to a vial containing a monolayer of cell line. The shell vial is centrifuged at a low speed and incubated for 24–48 hours. The tissue culture medium is removed, and the cells are stained using fluorescent-labeled anti-CMV antibod-ies and examined by a fluorescent microscope. The positive shell vial assay is the presumptive evidence of active CMV infection and has been found to be as sensitive as traditional tissue culture.
ELISA is a frequently used test to detect CMV IgM antibodies developed early during the course of illness and during reac-tivation of latent CMV infection. A fourfold or greater rise in antibody titer is diagnostic. The serology is useful for primary CMV infection, but not reliable for diagnosis of congenital CMV infection.
Histology: The presence of an enlarged cell that contains adense, central owl’s eye and basophilic intranuclear inclusion body is the characteristic feature of the cell infected by CMV. These cells are found in most tissues of the body and in the urine. These inclusion bodies can be readily seen on staining with hematoxylin–eosin or Papanicolaou’s staining. These cells are found in most tissues of the body and in the urine.