ABSTRACT
This study was performed to compare the replication of the pathogenic strain Brucella abortus 2308 in three trophoblastic cell lines derived bovine placentas at different gestational stages. The trophoblastic cell lines were obtained from a 13-15 day embryo, from 5-month placentomal tissue and from an 8-month extra-placentomal portion of the placenta. The infection rate was similar in all cell lines at 4 h. Colony-forming Units were counted at 4, 8, 12, 24 and 30 h post-inoculation. At 12, 16, 24 and 30 h B. abortus rapidly replicated within the 5-month and 8-month trophoblastic cell lines, but grew slowly within trophoblastic cells derived from embryonic tissue. Electron microscopic studies consistently showed clusters of B. abortus in trophoblastic cells derived from 5- and 8-month placentas, while few cells of the embryonic line were infected and these contained only 1-2 bacteria per cell. It was concluded that B. abortus can infect trophoblastic cells throughout the gestational period but bacterial multiplication does not occur in these cells before middle or late gestation.