Cytocidal viruses kill the cells in which they replicate. When a monolayer of cultured cells is infected with a small number of virions, their progeny will be released from the infected cells and will spread through the medium to infect distant fas well as adjacent) cells, so that eventually ail cells in the culture will be involved. The resulting cell damage is known as the cytopathic effect (CPE) of the virus, and the responsible virus is said to be cytopathogauc. The CPE can olten be observed by low-power light microscopy in unstained cell cultures (Figs 5-1 and 5-2A-C); fixation and staining of the cell monolayer may reveal further diagnostic details, notably inclusion bodies and syncytia The nature and speed of development of the cytopathic effect are characteristic of the particular virus involved and therefore represent important criteria for the preliminary identification of clinical isolates (see Chapter 12).
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