EGG INFECTIVITY ASSAY OF TRACHOMA VIRUS

SummaryOur method of egg infectivity assay for trachoma virus has been described. Because trachoma viruses grow more slowly in eggs (or are less lethal) than the related psittacosis viruses the highest dilutions which infect may not kill in 13 days. The egg infectious dose (based on demonstration of elementary bodies in dead eggs and those surviving 13 days) gave higher titers and more reproducible results than the egg lethal dose. Strain differences in egg pathogenicity were demonstrated. It took 5 infectious doses of the Bour and TW-3 strains to produce one lethal dose, while 80 infectious doses of the TW-1 strain equalled one lethal dose.