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

Abstract

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 16 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.