ISOLATION OF VIRUSES FROM CLINICAL SPECIMENS IN MICROTITRE PLATES WITH CELLS INOCULATED IN SUSPENSION

Virus isolation is essential for the provision of a full diagnostic vi rology service. Present methods are time consuming, expensive and rela tively inflexible for routine use. Our objective was to audit our exis ting virus isolation system and to develop a sensitive, flexible virus isolation system which could be adapted for use in a busy routine lab oratory which is required to provide a service for a wide range of cli nical situations. We carried out a pilot study which compared conventi onal roller tube monolayer cultures to a microplate system using cells inoculated in suspension and showed that the microplate method using extra cell lines could provide a more sensitive system for virus isola tion. This system was adapted for routine use using six cell lines ino culated in suspension and the results are presented for 2610 specimens for virus isolation and 972 for Clostridium difficile toxin (CDT) det ection. There were 516 viruses isolated and 229 specimens positive for CDT using this system. Polioviruses (92), echoviruses (35), coxsackie viruses (15) and untyped enteroviruses (13) were isolated in RMK, E6-v ero and RD cells. Adenoviruses (137) were isolated in HEp2 and EG-vero cells. Herpes simplex virus (HSV) was isolated from 149 specimens in E6-vero, FCL and HFF9 cells. Myxoviruses (35) and paramyxoviruses were isolated in RMK cells. HEp2 was the only cell line necessary to isola te the 33 respiratory syncytial viruses (RSV). Cytomegaloviruses (CMV) (2) and varicella tester (1) virus (VZV) were isolated only in the hu man fibroblast cell line HFF9, Rubella virus was isolated from a baby with congenital rubella in RMK, EG-vero and additionally in BGM cells, In conclusion; the use of cells inoculated in suspension in microtitr e plates for virus isolation was sensitive and convenient. It allowed the use of six cell lines for routine virus isolation without using ad ditional laboratory staff time. It improved turnaround times. It was a lso safer microbiologically than conventional isolation in tube monola yers. The precise identification of virus isolates was simplified.