Herpes simplex virus (HSV) types 1 and 2 (two strains each) were inactivated at different rates in vitro by 40 The present striking increase in the incidence of venereal diseases in the United States has been accompanied by a marked increase in observed genital infections caused by herpesviruses, mostly Herpesvirus hominis (herpes simplex virus [HSVJ) type 2. This rise in genital herpetic infections can be expected to produce an increasing exposure of newborns to the virus during passage through the birth canal, with a possible risk of serious illness (6, 7). The eyes of the neonate are one of the highly susceptible potential sites for infection with herpesviruses. However, immediately after delivery, 1% silver nitrate is instilled into the eyes of all newborns. This "Crede prophylaxis" is highly effective in controlling ocular infection due to gonococci acquired from the mother's genital tract (3). The question arises whether this silver nitrate prophylaxis might also have an effect on herpesvirus eye infection of the neonate acquired during passage through the birth canal. Cell culture. Vero (African green monkey kidney) cells were used in all culture procedures and for the preparation of infective pools of virus. The growth medium was Eagle's minimal essential medium (MEM) with the addition of 5% heat-inactivated fetal calf serum, nonessential amino acids, penicillin (100 units/ml), and streptomycin (100 ug/m4. When confluent monolayers were formed, the growth medium was replaced with maintenance medium (MM) consisting of MEM with 2% heat-inactivated fetal calf serum, nonessential amino acids, penicillin, and streptomycin.For plaque assays, the cells were grown in 16-oz (0.47-liter) prescription bottles. The cell sheets were removed with a mixture of 0.05% pancreatin, 0.05% ethylenediaminetetraacetate, and 0.05% trypsin in phosphate-buffered saline, and were resuspended in growth medium to a concentration of 1.5 million cells/5 ml. This volume was seeded into plastic tissue culture dishes (60 by 15 mm) and incubated at 37 C in 5% CO2 for 2 to 3 days. The medium was removed from confluent monolayers, and plates were inoculated with 0.2 ml of the material to be assayed. After a 2-to 2.5-h adsorption period at on May 12, 2018 by guest http://aac.asm.org/ Downloaded from