A rapid culture assay for examining measles virus infections from urine specimens

Background: Large numbers of measles virus (MV) specimens are processed in our laboratory each year as part of a molecular epidemiological study of MV in South Africa. The development of a sensitive, rapid virus isolation system is needed to cope with the number of specimens processed.

Objectives: A comparison was made of centrifugation-enhanced shell vial culture and standard tissue culture using B95a cells for the isolation of MV from throat swabs and urine.

Study design: The rapid method was initially evaluated using Schwarz vaccine virus and then compared to standard culture using throat swab specimens.

Results: The shell vial assay proved to be ten times more sensitive than standard culture in the initial evaluation. Of 43 throat swab specimens, 37 (86%) were positive and 6 (14%) negative in standard culture using B95a cells. The specimens were removed after adsorption in standard culture, frozen and then used in the shell vial assay. It was found that $\text{16}\text{27}$ were positive in the shell vial assay (24 of these 27 being positive in standard culture,) and 8 negative and 8 specimens gave an indeterminate result. For the 45 urine specimens used in the shell vial assay, 71% were positive, 11% negative and 18% gave an indeterminate result, due to too few cells being present for antigen determination by indirect fluorescent antibody assay. Results were obtained in 4 days, as opposed to the average of 14 days for confirmed isolation in standard culture.

Conclusion: Rapid culture substantially reduced total test time, was less labour-intensive and was as sensitive as standard culture for the isolation of measles virus from clinical specimens.