Trachoma viruses isolated in the United States. V. Growth rates and drug inhibition patterns in embryonated eggs.

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SummaryAll isolates of trachoma and inclusion conjunctivitis viruses from the United States in early egg passages grew in embryonated eggs at a rate similar to that of a Chinese isolate after many egg passages. During the phase of logarithmic growth there was an average increment of 1.3 logs of infective virus per day per gram of yolk sac. The size of inoculum determined the delay until the onset of logarithmic growth, but had no influence on rate of growth. The action of penicillin, tetracycline, or tylosin was fairly constant on each virus strain. However, there was much overlapping in drug-virus patterns so that the over-all effect of each drug could be depicted as a broad band. It now appears doubtful that the drug-susceptibility of virus strains is sufficiently fixed to serve as a genetic marker.