The inactivation of HEp-2 cell-associated poliovirus (Sabin 1) and coxsackievirus A9 was investigated in three experimental systems, using ozone as a disinfectant. The cell-associated viral samples were adjusted to a turbidity of 5 nephelometric turbidity units. The cell-associated poliovirus and coxsackievirus samples demonstrated survival in a continuous-flow ozonation system at applied ozone dosages of 4.06 and 4.68 mg/liter, respectively, for 30 s. Unassociated viral controls were inactivated by the application of 0.081 mg of ozone per liter for 10 s. Ultrasonic treatment of cell-associated enteric viruses did not increase inactivation of the cell-associated viruses. The batch reactor with a declining ozone residual did not effect total inactivation of either cell-associated enteric virus. These cell-associated viruses were completely inactivated after exposure to ozone in a batch reactor using continuous ozonation. Inactivation of cell-associated poliovirus required a 2-min contact period with an applied ozone dosage of 6.82 mg/liter and a residual ozone concentration of 4.70 mg/liter, whereas the coxsackievirus was completely inactivated after a 5-min exposure to an applied ozone dosage of 4.81 mg/liter with an ozone residual of 2.18 mg/liter. These data indicate that viruses associated with cells or cell fragments are protected from inactivation by ozone concentrations that readily inactivate purified virus. The cell-associated viral samples used in this research contained particles that were 10 to 15 microns in size. Use of a filtration system before ozonation would remove these particles, thereby facilitating inactivation of any remaining viruses associated with cellular fragments.

Abstract. An unidentified mycoplasma was isolated from cultures of Atlantic salmon (AS) cells and implicated as the cause of cytopathic effects (CPE). The agent did not visibly affect RTG‐2 cells. Experimental infection of RTG‐2 cells with Acholeplasma laidlawii resulted in increased cellular granularity and destruction. Scanning electron microscopic (SEM) examination of infected RTG‐2 and AS cultures revealed typical mycoplasmas distributed on cell surfaces and a marked effect on the cell surface topography, characterized by a loss of microvilli and cellular processes. SEM also revealed mycoplasmal contamination that was not detected by culturing. Comparisons of contaminated and uncontaminated RTG‐2 cells showed enhanced (2–100 fold) replication of infectious pancreatic necrosis virus (IPNV) and infectious haematopoietic necrosis virus (IHNV) in the presence of A, laidlawii.