The Plaque-forming Factor for Mink Lung Cells Present in Cytomegalovirus and Herpes-Zoster Virus Stocks Identified as Mycoplasma hyorhinis

1 Institut für Medizinische Virologie der Universität Heidelberg, Im Neuenheimer Feld 324 69 Heidelberg, F.R.G. 2 Institut für Virusforschung am Deutschen, Krebsforschungszentrum, Heidelberg, F.R.G. 3 Institut für biologische Schädlingsbekämpfung Biologische Bundesanstalt für Land und, Forstwirtschaft, Darmstadt, F.R.G. H. Gelderblom 4 , H. Delius 5 and R. H. Leach 6 4 Robert Koch Institut des Bundesgesundheitsamtes, West Berlin, F.R.G. 5 European Molecular Biology Laboratory, Heidelberg, F.R.G. 6 Mycoplasma Reference Laboratory Public Health Laboratory Service, Norwich, U.K. Previous investigation of the ability of cytomegalovirus and varicella-zoster virus to replicate in a variety of cell lines suggested that both virus types plaqued with high efficiency in mink lung cells. However, many of the virus isolates used appeared to be contaminated with mycoplasma. We now report that the observed cytopathic effect is due to a mycoplasma which grows lytically to high titre in mink lung cells, but is difficult to cultivate in cell-free media. The mycoplasma was plaque-purified and shown to contain DNA with a buoyant density of 1.684 g/ml, with restriction endonuclease patterns identical to the porcine mycoplasma M. hyorhinis . This was confirmed by serological identification. Keywords: Mycoplasma hyorhinis, restriction enzyme analysis Received 9 December 1980; accepted 23 February 1981.