Isolation of Chlamydia trachomatis by use of 5-iodo-2-deoxyuridine-treated cells

Irradiated McCoy cells have provided a useful technique for the isolation of Chlamydia trachomatis strains, among which are found the etiological agents of trachoma, inclusion conjunctivitis, and lymphogranuloma venereum. Because irradiation is not always readily available, 5-iodo-2-deoxyuridine (IUDR) treatment of cells was investigated as a substitute procedure. IUDR-treated cells were found to be as sensitive to C. trachomatis infection as were irradiated McCoy cells. Stock chlamydial strains gave similar titers of iodine-stained inclusions in either system. When cells treated with IUDR were compared with irradiated cells for the isolation of C. trachomatis from clinical specimens, 5 of 138 specimens yielded isolates in IUDR-treated cells not found in irradiated ones, and one isolate was obtained from irradiated but not from IUDR-treated cells. In those 56 cases where inclusions were seen in both systems, there were significantly more inclusions in IUDR-treated than in irradiated cells. Although this series of cultures is too small to determine whether IUDR-treated cells are superior to irradiated ones for the isolation of C. trachomatis, the data indicate that IUDR treatment is at least equally effective.