Effects of sonication of clinical specimens on detection of cytomegalovirus in shell vial cultures.
BACKGROUND
The centrifugation-enhanced shell vial (SV) method of virus culturing has decreased the time to laboratory detection of many viruses, and has become the principal method for the rapid detection of cytomegalovirus (CMV) in clinical specimens.


OBJECTIVE
To examine the use of sonication and centrifugation of clinical specimens as a means of optimizing the sensitivity of SV detection of CMV, decreasing the toxicity of specimens to the SV monolayer, and facilitating the examination and interpretation of SV monolayers.


METHODS
A total of 350 clinical specimens submitted for CMV culture were processed and then divided in half, with one-half sonicated for 1 min in a cup-horn-equipped sonicator, and the other half left unsonicated. Sonicated specimens were centrifuged to recover a cell-free supernatant. SVs containing MRC-5 fibroblast monolayers were inoculated with either the unsonicated whole specimen or the cell-free supernatant, and were stained with monoclonal antibodies directed against the immediate-early antigen of CMV after 24 and 48 h of incubation.


RESULTS
While no significant difference was observed in the overall number of specimens in which CMV was detected following sonication, sonication did afford a 31% increase in the number of CMV-positive specimens detected at 24 h. A significant reduction in toxicity of all specimens except for blood was observed for the sonicated specimens, although sonication of blood increased the number of blood specimens toxic to the monolayer by 40%. Use of the cell-free inoculum following sonication facilitated microscopic examination and interpretation of SV monolayers without adversely affecting the sensitivity of the culture.


CONCLUSIONS
Sonication of clinical specimens prior to shell vial culturing for CMV is beneficial and can help to reduce specimen toxicity, facilitate interpretation of monolayers, and allow the earlier detection of a positive specimen.
Engler
H D
HD
Microbiology Service, Clinical Pathology Department, Warren Grant Magnuson Clinical Center, National Institutes of Health, Building 10, Room 2C-385, Bethesda, MD 20892-1508, USA. hengler@nih.gov
Selepak
S T
ST
Callaway
J
J