What is the role of viral culture in the workup of viral pneumonia?

Updated: Mar 24, 2021
  • Author: Zab Mosenifar, MD, FACP, FCCP; Chief Editor: John J Oppenheimer, MD  more...
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Answer

Viral pneumonia can be diagnosed by isolation and identification of the pathogen through viral culture.

Tissue from the upper or lower respiratory tract, sputum samples, and samples obtained by nasopharyngeal washing, bronchoalveolar lavage, and biopsy may be submitted for viral culture. The use of an appropriate viral transport medium is required. This consists of enriched broth containing antibiotics and a protein substrate.

Viral cultures are performed on various cell lines (eg, monkey kidney cells, diploid fibroblasts). The cell cultures are incubated at 35°C and are examined microscopically on alternate days for an incubation period of 14 days.

The cultures are examined for cytopathogenic effects and for evidence of viral growth. The cytopathogenic effect is the formation of syncytial collections of multinucleated giant cells and rarely is virus specific. Viral growth is detected through hemadsorption testing by demonstrating adherence of red blood cells to the cultured cell monolayer of infected tissue.

Further identification of viruses is accomplished using immunofluorescence (direct or indirect) methods or nucleic acid probes. These techniques are used to identify the specific virus in cell cultures.

Viral cultures are of lower yield in RSV infection (viral lability, lower titers in samples), human metapneumovirus (hMPV) infection, and coronavirus infection (special growth requirements).

Modified cell culture methods called shell vial culture systems are able to detect certain slow-growing viruses. Shell vial culture systems are used widely for earlier detection of CMV, RSV, herpes simplex virus (HSV), adenovirus, influenza viruses, parainfluenza virus (PIV), and other viral pathogens.

In this technique, the prepared clinical specimens are inoculated on to adherent cell monolayers grown on round coverslips in small vials. The vials are centrifuged at low speed for one hour, after which fresh culture medium is added. Next, the vials are incubated and examined serially to detect viral antigen or DNA expression. Results typically become available in 2-3 weeks.


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