FIG. 1.

C. muridarum Nigg successfully competes with CM972 in vitro but not with CM3.1. (A) Competition with CM972. L929 fibroblasts were infected without centrifugation with C. muridarum Nigg, with CM972, or with a mixed inoculum and were incubated for 40 h before harvest. This process was repeated 5 times, using 1/10 of the prior passage volume as the inoculum each time. Samples from each passage were subsequently infected into L929 fibroblasts with centrifugation and incubated for 40 h before being fixed and stained with iodine to detect Nigg (iodine-positive) and CM972 (iodine-negative) inclusions. (B) Competition with CM3.1. L929 fibroblasts were infected (without centrifugation) with C. muridarum Nigg or CM3.1 or with a mixed inoculum for passage and analysis as described above. Data presented were obtained from the simultaneous counting and iodine scoring of 150 to 200 inclusions/well, with two replicates per passage. Each experiment was performed twice.