Susceptibility of McCoy cells to infection by Chlamydia psittaci

Abstract

Irradiated McCoy cell cultures were susceptible to infection with all of six psittacosis isolates tested. The organisms could be demonstrated readily in infected mouse brain suspensions by inoculation (0.5 ml) of irradiated cells with dilutions killing 50% of weanling mice inoculated intracerebrally (0.03 ml). Staining of the inoculated monolayers with Gimenez or fluorescent antibody stain and inspecting microscopically for presence of the organism was a more sensitive test than mere observation of the cultures for cytopathic effect. Irradiation of McCoy cells increased their susceptibility.An advantage of the McCoy system over the use of mice is that it requires only a 7-day test period rather than a 21-day test period. One disadvantage is the need to stain and examine each inoculated culture; in addition, irradiation facilities must be available.