Differential Recovery of Cytomegalovirus from Cellular and Supernatant Components of Bronchoalveolar Lavage Specimens

The recovery of cytomegalovirus from bronchoalveolar lavage (BAL) specimens was compared after inoculation of MRC-5 tube and shell vial cell cultures with four different BAL preparations. Analysis of culture results obtained with 55 cytomegalovirus culture-positive samples showed significant differences in the ability to isolate virus from the supernatant and cellular components of these specimens. There was a 52% reduction in cytomegalovirus recovery and a significant delay in the development of cytopathic effect in cultures inoculated with the cellular component of BAL specimens when compared to cultures inoculated with crude BAL cells and fluid. The mean time for detection of cytopathic effect was 11.8 days in tubes inoculated with crude BAL and 18.2 days for tubes inoculated with BAL cells. A similar effect was observed using a rapid shell vial culture technique. A 39% reduction in the number of isolates and a 57% reduction in the number of positive cells were observed in vials inoculated with cells when compared to cultures inoculated with crude BAL. By contrast, using cell-free BAL supernatant as inoculum did not reduce the number of positive cultures or delay development of cytopathic effect. The results suggest that in most BAL specimens, cytomegalovirus is associated with the cell-free, rather than the cellular, component. Although BAL cell concentrates frequently are used for cultivation of viruses from BAL, our results showed that the use of these preparations results in a significant number of false-negative cytomegalovirus cultures.